These lectures feature speakers from around the country and globe. Each colloquium lasts about an hour and gives you a deeper understanding of the types of physics and astronomy researching going on around the world.
Colloquia will be held in a hybrid format and a recurring Zoom link is provided to access the virtual format.
If you are interested in being added to our e-mail distribution list regarding upcoming colloquia, please contact Ms. Beth Powell via e-mail at mepowell@mailbox.sc.edu. We appreciate your interest!
Upcoming Colloquia (Fall 2023):
Date |
Speaker |
Title of Colloquium Talk |
| August 31, 2023 | Welcome Event for Graduate Students | |
| September 7, 2023 | Dr. Michael Kohl Department of Physics Hampton University Hampton, VA |
TBA |
| September 14, 2023 | Dr. Tim Mousseau Department of Biological Sciences University of South Carolina Columbia, SC |
TBA |
| September 21, 2023 | Dr. Wolfgang Lorenzon Department of Physics University of Michigan Ann Arbor, MI |
TBA |
| September 28, 2023 | Dr. David Singh Department of Physics and Astronomy University of Missouri Columbia, MO |
TBA |
| October 5, 2023 | Dr. Edward Kolb Department of Astronomy and Astrophysics University of Chicago Chicago, IL |
TBA |
| October 12, 2023 | Dr. Ted Dallas Department of Biological Sciences University of South Carolina Columbia, SC |
TBA |
| October 19, 2023 | Fall Break | |
| October 26, 2023 | Adam Taylor Intel |
TBA |
| November 2, 2023 | Dr. David Mandrus Department of Materials Science and Engineering University of Tennessee Knoxville, TN |
TBA |
| November 9, 2023 | Dr. John Perdew Department of Physics Temple University Philadelphia, PA |
TBA |
| November 16, 2023 | Dr. Vince Guiseppe Oak Ridge National Laboratory Oak Ridge, TN |
TBA |
| November 23, 2023 | Thanksgiving Break | |
| November 30, 2023 | Dr. David Ceperly Department of Physics University of Illinois Urbana, IL |
TBA |
| December 7, 2023 | Departmental New Year’s party! |
________________________________________________________________________________________
Recent Colloquia:
Dr. Sebastian König
Department of Physics
North Carolina State University
Raleigh, NC
Research Profile
Abstract:
Nuclear physics is connected to many different areas of physics, spanning arcs from particle physics all the way to astronomy. A solid understanding of nuclear systems from first principles, that is, based on Quantum Chromodynamics as the fundamental theory of the strong interaction, is therefore of great importance. In this talk, I will present an overview of how to address this challenge using simulations of nuclear systems in finite volume. This approach, which is in fact not limited to nuclear physics, is based on the observation that the real-world properties of quantum systems are encoded in how their discrete energy levels change when the size of the simulation volume is varied, thus providing a powerful theoretical tool.
YouTube Recording
Department of Physics
North Carolina State University
Raleigh, NC
Research Profile
Abstract:
Nuclear physics is connected to many different areas of physics, spanning arcs from particle physics all the way to astronomy. A solid understanding of nuclear systems from first principles, that is, based on Quantum Chromodynamics as the fundamental theory of the strong interaction, is therefore of great importance. In this talk, I will present an overview of how to address this challenge using simulations of nuclear systems in finite volume. This approach, which is in fact not limited to nuclear physics, is based on the observation that the real-world properties of quantum systems are encoded in how their discrete energy levels change when the size of the simulation volume is varied, thus providing a powerful theoretical tool.
YouTube Recording
Dr. Qui Wang
Department of Mathematics
University of South Carolina
Columbia, SC
Research Profile
Abstract:
Professor Lars Onsager was awarded 1968's Nobel Prize for Chemistry for the discovery of reciprocal relations, named after him, and basic to irreversible thermodynamics. In this talk, I will define and discuss the generalized Onsager principle (GOP) as a fundamental modeling tool for nonequilibrium thermodynamical systems and use simple examples to show how one can use GOP to develop mathematical models for nonequilibrium systems in, for example, materials sciences and life science. Then, I will present a systematic way to design structure-preserving numerical algorithms for thermodynamically consistent nonequilibrium systems guided by GOP.
YouTube Recording
Department of Mathematics
University of South Carolina
Columbia, SC
Research Profile
Abstract:
Professor Lars Onsager was awarded 1968's Nobel Prize for Chemistry for the discovery of reciprocal relations, named after him, and basic to irreversible thermodynamics. In this talk, I will define and discuss the generalized Onsager principle (GOP) as a fundamental modeling tool for nonequilibrium thermodynamical systems and use simple examples to show how one can use GOP to develop mathematical models for nonequilibrium systems in, for example, materials sciences and life science. Then, I will present a systematic way to design structure-preserving numerical algorithms for thermodynamically consistent nonequilibrium systems guided by GOP.
YouTube Recording
Dr. Maxim Tsoi
Department of Physics
University of Texas at Austin
Austin, TX
Research Profile
Abstract:
Spintronics is built on a complementary set of phenomena in which the magnetic configuration of a system influences its transport properties and vice versa. In ferromagnetic systems, these interconnections are exemplified by Giant Magnetoresistance (GMR) – where the system’s resistance depends on the relative orientation of magnetic moments in constituent ferromagnetic parts, and Spin Transfer Torque (STT) – in which an electrical current can perturb the system’s magnetic state. Such transport phenomena provide a means to read and write information in magnetic memory devices like STTRAM.
Similar interconnections between magnetism and transport were proposed to occur in systems where ferromagnetic components are replaced with antiferromagnets (AFMs), thus leading to a new field of research – antiferromagnetic spintronics, which exploits unique properties of AFMs to create new and improved functionalities in spintronic devices [1]. For instance, AFMs can be used in magnetic memories to achieve higher speeds and increased stability thanks to their high natural frequencies and zero net magnetization. Initial experiments with metallic AFMs (FeMn, IrMn) were promising in demonstrating the AFM analogue of STT [2]. However, the limited choice of metallic AFMs calls to explore insulating/semiconducting materials with abundant AFM presence.
In our research we focus on AFM transition metal oxides (TMO). TMOs are known to exhibit an extremely wide range of magnetic and transport properties. Most importantly, their properties can be tuned using various external stimuli like applied magnetic and electric fields. For instance, the magnetic field was found to produce a very large anisotropic magnetoresistance in AFM iridates [3] while the electrical bias can drive a significant continuous reduction in TMO’s resistivity followed by an abrupt resistive switching (Sr2IrO4, Sr3Ir2O7, La2NiO4, Ca2RuO4). The observed resistivity variations were attributed to electric-field-driven structural distortions [4-6]. Now we use an ultra-sensitive capacitive displacement meter to monitor the field-induced lattice distortions in situ. We observe that the crystal contraction/expansion is strongly correlated with the resistive switching [7]. Our results provide unequivocal evidence that the resistive switching is related to structural distortions and support the idea of voltage controlled TMOs in nonvolatile memory and logic.
[1] V. Baltz et al. Rev. Mod. Phys. 90, 015005 (2018); [2] Z. Wei et al., Phys. Rev. Lett. 98, 116603 (2007); [3] C. Wang et al. Phys. Rev. X 4, 041034 (2014); [4] C. Wang et al. Phys. Rev. B 92, 115136 (2015); [5] H. Seinige et al. Phys. Rev. 94, 214434 (2016); [6] S. Shen et al. J. Appl. Phys. 122, 245108 (2017); [7] S. Shen et al. J. Phys. D: Appl. Phys. 53, 075302 (2020).
Youtube Recording
Department of Physics
University of Texas at Austin
Austin, TX
Research Profile
Abstract:
Spintronics is built on a complementary set of phenomena in which the magnetic configuration of a system influences its transport properties and vice versa. In ferromagnetic systems, these interconnections are exemplified by Giant Magnetoresistance (GMR) – where the system’s resistance depends on the relative orientation of magnetic moments in constituent ferromagnetic parts, and Spin Transfer Torque (STT) – in which an electrical current can perturb the system’s magnetic state. Such transport phenomena provide a means to read and write information in magnetic memory devices like STTRAM.
Similar interconnections between magnetism and transport were proposed to occur in systems where ferromagnetic components are replaced with antiferromagnets (AFMs), thus leading to a new field of research – antiferromagnetic spintronics, which exploits unique properties of AFMs to create new and improved functionalities in spintronic devices [1]. For instance, AFMs can be used in magnetic memories to achieve higher speeds and increased stability thanks to their high natural frequencies and zero net magnetization. Initial experiments with metallic AFMs (FeMn, IrMn) were promising in demonstrating the AFM analogue of STT [2]. However, the limited choice of metallic AFMs calls to explore insulating/semiconducting materials with abundant AFM presence.
In our research we focus on AFM transition metal oxides (TMO). TMOs are known to exhibit an extremely wide range of magnetic and transport properties. Most importantly, their properties can be tuned using various external stimuli like applied magnetic and electric fields. For instance, the magnetic field was found to produce a very large anisotropic magnetoresistance in AFM iridates [3] while the electrical bias can drive a significant continuous reduction in TMO’s resistivity followed by an abrupt resistive switching (Sr2IrO4, Sr3Ir2O7, La2NiO4, Ca2RuO4). The observed resistivity variations were attributed to electric-field-driven structural distortions [4-6]. Now we use an ultra-sensitive capacitive displacement meter to monitor the field-induced lattice distortions in situ. We observe that the crystal contraction/expansion is strongly correlated with the resistive switching [7]. Our results provide unequivocal evidence that the resistive switching is related to structural distortions and support the idea of voltage controlled TMOs in nonvolatile memory and logic.
[1] V. Baltz et al. Rev. Mod. Phys. 90, 015005 (2018); [2] Z. Wei et al., Phys. Rev. Lett. 98, 116603 (2007); [3] C. Wang et al. Phys. Rev. X 4, 041034 (2014); [4] C. Wang et al. Phys. Rev. B 92, 115136 (2015); [5] H. Seinige et al. Phys. Rev. 94, 214434 (2016); [6] S. Shen et al. J. Appl. Phys. 122, 245108 (2017); [7] S. Shen et al. J. Phys. D: Appl. Phys. 53, 075302 (2020).
Youtube Recording
Dr. David Tanner
Department of Physics,
University of Florida
Gainesville, FL
Research Profile
Abstract:
The Any Light Particle Search II (ALPS II) is an experiment currently being commissioned at DESY in Hamburg, Germany. ALPS II uses a light-shining-through-a-wall approach to search for axion-like particles. Laser light (a photon beam) passing through a strong magnetic field will in part be converted to a beam of axions. A material wall will block the laser light, but the weakly interacting axions pass through unhindered. There, they enter a second strong magnet where they will in part be converted back to photons. When the photon light is detected, it appears that it shined through the wall. ALPS II represents a significant step forward for these types of experiments as it will use 24 superconducting dipole magnets, along with dual high-finesse, 122 m long optical cavities. The experiment will be the first implementation of the idea, proposed many years ago, to use optical cavities before and after the wall to increase the power of the regenerated photon signal. This concept will allow the experiment to achieve a sensitivity in terms of the coupling between axion-like particles and photons down to gaγγ = 2 × 10−11 GeV−1 for masses below 0.1 meV, more than three orders of magnitude beyond the sensitivity of previous, purely laboratory-based, axion search experiments.
YouTube Recording
Department of Physics,
University of Florida
Gainesville, FL
Research Profile
Abstract:
The Any Light Particle Search II (ALPS II) is an experiment currently being commissioned at DESY in Hamburg, Germany. ALPS II uses a light-shining-through-a-wall approach to search for axion-like particles. Laser light (a photon beam) passing through a strong magnetic field will in part be converted to a beam of axions. A material wall will block the laser light, but the weakly interacting axions pass through unhindered. There, they enter a second strong magnet where they will in part be converted back to photons. When the photon light is detected, it appears that it shined through the wall. ALPS II represents a significant step forward for these types of experiments as it will use 24 superconducting dipole magnets, along with dual high-finesse, 122 m long optical cavities. The experiment will be the first implementation of the idea, proposed many years ago, to use optical cavities before and after the wall to increase the power of the regenerated photon signal. This concept will allow the experiment to achieve a sensitivity in terms of the coupling between axion-like particles and photons down to gaγγ = 2 × 10−11 GeV−1 for masses below 0.1 meV, more than three orders of magnitude beyond the sensitivity of previous, purely laboratory-based, axion search experiments.
YouTube Recording
Dr. Kai Schweda, GSI
Darmstadt and CERN
Heidelberg, Germany
Research Profile
Abstract:
The Large Hadron Collider (LHC) at CERN is the most powerful particle accelerator in the world. ALICE is one of the four large-scale experiments at LHC with about 1000 scientists from 40 different nations. In ultrarelativistic collisions of nuclei as heavy as lead, an extraordinary state of matter at temperatures of more than 2 trillion Kelvin arises, which is similar to the early universe a few microseconds after the big bang. This presentation provides an insight into the cutting-edge technology ALICE uses in order to detect and identify subatomic particles created in these collisions. The resulting huge amounts of data require innovative solutions with the most modern computers and algorithms. Some selected physics highlights are presented. An outlook for ALICE into the 2030es is given.
YouTube Recording
Darmstadt and CERN
Heidelberg, Germany
Research Profile
Abstract:
The Large Hadron Collider (LHC) at CERN is the most powerful particle accelerator in the world. ALICE is one of the four large-scale experiments at LHC with about 1000 scientists from 40 different nations. In ultrarelativistic collisions of nuclei as heavy as lead, an extraordinary state of matter at temperatures of more than 2 trillion Kelvin arises, which is similar to the early universe a few microseconds after the big bang. This presentation provides an insight into the cutting-edge technology ALICE uses in order to detect and identify subatomic particles created in these collisions. The resulting huge amounts of data require innovative solutions with the most modern computers and algorithms. Some selected physics highlights are presented. An outlook for ALICE into the 2030es is given.
YouTube Recording
Dr. John Singleton, Staff Member and LANL Fellow
National High Magnetic Field Lab
Tallahassee, FL
Research Profile
Abstract:
From an early age, we are taught that metals are good conductors of electricity and heat but that insulators are not. At high school, we learn the reason; metals contain vast numbers of charged electrons that are free to move and carry heat and current, whereas insulators do not. At college, we find out that electrons are fermions, and perhaps comprehend Fermi-Dirac statistics, leading to the well-known definition that “a metal is a solid with a Fermi surface”. The Fermi surface is the constant-energy surface which at zero temperature separates the occupied electron states from the empty in momentum space; if we know the size and shape of a metal’s Fermi surface, we understand how its free electrons behave and hence can account for almost all of its electrical, thermal and magnetic properties.
Over the past five years, this comforting picture has been upset by experiments on the compounds YbB12 and SmB6 at high magnetic fields and low temperatures. Though these materials are electrical insulators, they exhibit an oscillatory effect in magnetic field that is smoking-gun evidence for a Fermi surface, i.e., it is usually seen only in metals. Equally striking is the low-temperature thermal conductivity of YbB12, which looks as though it comes from a large concentration of free electrons. Somehow, mobile fermions are present and able to carry heat almost as well as in a conventional metal but are unable to conduct electricity!
In this talk, I will describe our recent data from YbB12 in magnetic fields of up to 75 T. These and earlier results suggest a new state of matter that includes mobile, electrically neutral fermions. The latter may be Majorana fermions, particles that are their own antiparticle hypothesized by Ettore Majorana in 1937; they remain a controversial and active topic in particle physics (e.g., is the neutrino a Dirac or Majorana fermion?). In condensed-matter physics, interactions may cause electrons to masquerade as Majorana fermions. If this is true, it would be another instance of the fruitful cross-fertilization between condensed-matter physics and particle physics that has enhanced our knowledge of magnetic monopoles, Dirac and Weyl fermions and Higgs bosons.
YouTube Recording
National High Magnetic Field Lab
Tallahassee, FL
Research Profile
Abstract:
From an early age, we are taught that metals are good conductors of electricity and heat but that insulators are not. At high school, we learn the reason; metals contain vast numbers of charged electrons that are free to move and carry heat and current, whereas insulators do not. At college, we find out that electrons are fermions, and perhaps comprehend Fermi-Dirac statistics, leading to the well-known definition that “a metal is a solid with a Fermi surface”. The Fermi surface is the constant-energy surface which at zero temperature separates the occupied electron states from the empty in momentum space; if we know the size and shape of a metal’s Fermi surface, we understand how its free electrons behave and hence can account for almost all of its electrical, thermal and magnetic properties.
Over the past five years, this comforting picture has been upset by experiments on the compounds YbB12 and SmB6 at high magnetic fields and low temperatures. Though these materials are electrical insulators, they exhibit an oscillatory effect in magnetic field that is smoking-gun evidence for a Fermi surface, i.e., it is usually seen only in metals. Equally striking is the low-temperature thermal conductivity of YbB12, which looks as though it comes from a large concentration of free electrons. Somehow, mobile fermions are present and able to carry heat almost as well as in a conventional metal but are unable to conduct electricity!
In this talk, I will describe our recent data from YbB12 in magnetic fields of up to 75 T. These and earlier results suggest a new state of matter that includes mobile, electrically neutral fermions. The latter may be Majorana fermions, particles that are their own antiparticle hypothesized by Ettore Majorana in 1937; they remain a controversial and active topic in particle physics (e.g., is the neutrino a Dirac or Majorana fermion?). In condensed-matter physics, interactions may cause electrons to masquerade as Majorana fermions. If this is true, it would be another instance of the fruitful cross-fertilization between condensed-matter physics and particle physics that has enhanced our knowledge of magnetic monopoles, Dirac and Weyl fermions and Higgs bosons.
YouTube Recording
Dr. George Androulakis, Professor
Department of Mathematics
University of South Carolina
Research Profile
Abstract:
In this talk, I plan to give an introduction to Quantum Information by presenting parts from one of my latest research works. Quantum Information is a branch of science which examines quantum phenomena but often draws inspiration from classical information theory. I will use one of my latest research projects to illustrate these parallel fields. I will try to make my talk accessible to the graduate students who may choose to work on this exciting and fast-growing research field.
Department of Mathematics
University of South Carolina
Research Profile
Abstract:
In this talk, I plan to give an introduction to Quantum Information by presenting parts from one of my latest research works. Quantum Information is a branch of science which examines quantum phenomena but often draws inspiration from classical information theory. I will use one of my latest research projects to illustrate these parallel fields. I will try to make my talk accessible to the graduate students who may choose to work on this exciting and fast-growing research field.
Dr. Christopher Jarzynski, Distinguished University Professor
Department of Physics and the Department of Chemistry and Biochemistry
University of Maryland
Research Profile
Abstract:
Every major galaxy seems to contain a supermassive black hole at its center. About 1% of these supermassive black holes are actively accreting gas from surrounding material and are Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit “thermodynamic-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work, and single molecules exhibit hysteresis when manipulated using optical tweezers. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the challenges and recent progress – both theoretical and experimental – associated with addressing these questions. Along the way, my talk will touch on non-equilibrium fluctuations, “violations” of the second law, the thermodynamic arrow of time, nanoscale feedback control, strong system-environment coupling, and quantum thermodynamics.
YouTube Recording
Department of Physics and the Department of Chemistry and Biochemistry
University of Maryland
Research Profile
Abstract:
Every major galaxy seems to contain a supermassive black hole at its center. About 1% of these supermassive black holes are actively accreting gas from surrounding material and are Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit “thermodynamic-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work, and single molecules exhibit hysteresis when manipulated using optical tweezers. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the challenges and recent progress – both theoretical and experimental – associated with addressing these questions. Along the way, my talk will touch on non-equilibrium fluctuations, “violations” of the second law, the thermodynamic arrow of time, nanoscale feedback control, strong system-environment coupling, and quantum thermodynamics.
YouTube Recording
Dr. Ed Cackett, Professor and Interim Chair
Department of Physics and Astronomy
Wayne State University
Research Profile
Abstract:
Every major galaxy seems to contain a supermassive black hole at its center. About 1% of these supermassive black holes are actively accreting gas from surrounding material and are referred to as Active Galactic Nuclei (or AGNs). The gravitational potential energy liberated as this gas sinks towards the black hole (‘accretes’) makes AGNs some of the most luminous objects in the Universe. Accretion is an important process since the energy that feeds back into the host galaxy has an important influence on its evolution. Accretion is thought to take place via an optically thick, geometrically thin ‘accretion disk’. However, the angular size of these disks is (generally) too small to be resolved with current technology. I will describe how we use a technique called reverberation mapping, that swaps spatial resolution for time resolution, to infer the size of these accretion disks and better understand what happens in the region closest to the supermassive black hole in AGNs.
YouTube Recording
Department of Physics and Astronomy
Wayne State University
Research Profile
Abstract:
Every major galaxy seems to contain a supermassive black hole at its center. About 1% of these supermassive black holes are actively accreting gas from surrounding material and are referred to as Active Galactic Nuclei (or AGNs). The gravitational potential energy liberated as this gas sinks towards the black hole (‘accretes’) makes AGNs some of the most luminous objects in the Universe. Accretion is an important process since the energy that feeds back into the host galaxy has an important influence on its evolution. Accretion is thought to take place via an optically thick, geometrically thin ‘accretion disk’. However, the angular size of these disks is (generally) too small to be resolved with current technology. I will describe how we use a technique called reverberation mapping, that swaps spatial resolution for time resolution, to infer the size of these accretion disks and better understand what happens in the region closest to the supermassive black hole in AGNs.
YouTube Recording
Dr. Alexander Monin, Assistant Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
In this talk, I present a subjective perspective on challenges theoretical physics faces at the moment. After giving an introductory overview of the current situation in High Energy Physics with its successes and failures, I will argue that one of the most pressing issues in theoretical physics is harnessing non-perturbative dynamics. I will show that non-perturbativity is not a vice of strongly interacting systems alone, it also plagues models at weak coupling when large quantum numbers are present. I will give a prescription for how these difficulties can be circumvented in the latter case and illustrate the method with several examples from quantum mechanics and conformal field theories. I will also briefly talk about semi-analytic approaches to non-perturbative phenomena in theories with arbitrary coupling.
YouTube Recording
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
In this talk, I present a subjective perspective on challenges theoretical physics faces at the moment. After giving an introductory overview of the current situation in High Energy Physics with its successes and failures, I will argue that one of the most pressing issues in theoretical physics is harnessing non-perturbative dynamics. I will show that non-perturbativity is not a vice of strongly interacting systems alone, it also plagues models at weak coupling when large quantum numbers are present. I will give a prescription for how these difficulties can be circumvented in the latter case and illustrate the method with several examples from quantum mechanics and conformal field theories. I will also briefly talk about semi-analytic approaches to non-perturbative phenomena in theories with arbitrary coupling.
YouTube Recording
Dr. Lori Ziolkowski, Associate Professor
School of the Earth, Ocean and Environment
University of South Carolina
Research Profile
Abstract:
Physical processes are central to the climate system. Examples are the global energy balance, why climate changed in the past, how heat mixes within the system, and potential contemporary solutions to climate change. In this talk, I will discuss a few different aspects of the climate system with an eye to how physics is a key component. The talk will start with the fundamentals of how a planet’s atmosphere is critical for the surface temperature, which is relevant for exoplanet research. Then we will walk through why climate changed in the past versus today. Then the work of the recent Nobel laureates studying the physics of mixing within the climate system will be discussed. Finally, the talk will close with an examination of what the Earth’s climate may look like in the next half century and possible interventions that alter the physics of the energy system.
YouTube Recording
School of the Earth, Ocean and Environment
University of South Carolina
Research Profile
Abstract:
Physical processes are central to the climate system. Examples are the global energy balance, why climate changed in the past, how heat mixes within the system, and potential contemporary solutions to climate change. In this talk, I will discuss a few different aspects of the climate system with an eye to how physics is a key component. The talk will start with the fundamentals of how a planet’s atmosphere is critical for the surface temperature, which is relevant for exoplanet research. Then we will walk through why climate changed in the past versus today. Then the work of the recent Nobel laureates studying the physics of mixing within the climate system will be discussed. Finally, the talk will close with an examination of what the Earth’s climate may look like in the next half century and possible interventions that alter the physics of the energy system.
YouTube Recording
Dr. Joseph E. Johnson, Distinguished Professor Emeritus
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
Quantum Theory (QT), Special Relativity (SR), and the Standard Model (SM) are framed
and well-established in terms of Lie algebras. But Einstein’s theory of gravitation,
General Relativity (GR), while also well-established, is framed in terms of nonlinear
differential equations in Riemannian Geometry (RG) for the space-time metric and space-time
variables. We seek to provide a more general framework for RG to potentially support
an integration of GR, QT, and the SM by generalizing Lie algebras mathematically and
thus integrating all forces in a single framework.
After (1) an introduction on notation, the colloquium will begin with (2) a purely mathematical presentation where (RG) will be reframed
as a Generalized Lie algebra (GLA) allowing the equations of both (RG) and then (GR)
to be expressed as commutation relations among fundamental operators. Then (3), applying
this framework to physics, Einstein’s equations for GR can be expressed in terms of
just operators and commutators in this generalized Lie algebra in a position diagonal
representation of this noncommutative algebra of operators.
Our consequences are (a) that the (effective momentum) translation operators, D, now
contain the gravitational as well as the standard model of the electroweak and strong
forces on equal footings. (b) The SM gauge transformations are automatically altered
by the inclusion of the gravitational metric. (c) A generalized uncertainty principle
is predicted that might alter virtual pair creation in strong gravitational fields
leading to observable spectral shifts in H. (d) It is shown that there is a second
set of equations parallel to those of Einstein that relate the divergentless angular
momentum density to a divergentless commutator expression containing the Einstein
tensor. Finally, (e) the metric operator is shown to be the measure of the interference
of the generalized momentum and position operators in a curved space-time. (f) There
are no restrictions on the dimensionality of space-time thus allowing for hidden dimensions
such as string theory. Future directions are discussed.
YouTube Recording
YouTube Recording
Dr. Ignatios Antoniadis
Laboratoire de Physique Théorique et Hautes Énergies
Sorbonne Université
Paris, France
Research Profile
Abstract:
Laboratoire de Physique Théorique et Hautes Énergies
Sorbonne Université
Paris, France
Research Profile
Abstract:
Particle physics studies the elementary constituents of matter and their fundamental
forces. Very short distances are explored by particle collisions at very high energies,
creating conditions similar to those governing the Universe just after the Big Bang.
This is the reason that the same physics is also explored by cosmology through observations
on the sky at very large distances.
The current theory of particle physics, called Standard Model, provides an accurate
description of all known physical phenomena in the microcosmos. On the other hand,
the Standard Model of cosmology describes very well observations, confirmed recently
by the Planck satellite experiments, pointing to the existence of a new dark sector
of the Universe containing dark matter and dark energy.
I will discuss the problem of scale hierarchies in particle physics and cosmology
and propose ways to address it. In particular, I will present a framework of unifying
two theoretical proposals beyond the standard models of particle physics and cosmology:
supersymmetry and inflation, by identifying the inflation boson with the superpartner
of the Goldstone fermion of spontaneous supersymmetry breaking and will describe its
phenomenological consequences.
YouTube Recording
YouTube Recording
Dr. Gang Cao, Professor
Department of Physics
University of Colorado Boulder
Boulder, CO
Research Profile
Abstract:
Colossal magnetoresistance is an extraordinary enhancement of the electric conductivity in the presence of a magnetic field, an important property of matter that has been studied for decades. It is conventionally associated with a magnetic-field-induced spin polarization, which drastically reduces spin scattering, thus electric resistance. Our earlier studies uncover an intriguing exception to this rule in that the electric resistivity in a magnetic insulator is reduced by up to 7 orders of magnitude only when a spin polarization is absent [1]. Here I report a newly identified quantum state in a honeycomb material where internal loop currents flowing along edges of crystal unit cells dictate electric conductivity, providing a key element driving the novel colossal magnetoresistance [2]. The unique nature and control of the exotic quantum state, along with implications of this discovery, will be presented and discussed after a brief review of conventional colossal magnetoresistance and loop currents in other materials.
References:
1. Colossal magnetoresistance via avoiding fully polarized magnetization in ferrimagnetic insulator Mn3Si2Te6, Yifei Ni, Hengdi Zhao, Yu Zhang, Bing Hu, Itamar Kimchi and Gang Cao, Letter of Phys. Rev. B 103, L161105 (2021); DOI:10.1103/PhysRevB.103.L161105
2. Control of chiral orbital currents in a colossal magnetoresistance material, Yu Zhang, Yifei Ni, Hengdi Zhao, Sami Hakani, Feng Ye, Lance DeLong, Itamar Kimchi, and Gang Cao, Nature, October 12, 2022, DOI: 10.1038/s41586-022-05262-3
YouTube Recording
Department of Physics
University of Colorado Boulder
Boulder, CO
Research Profile
Abstract:
Colossal magnetoresistance is an extraordinary enhancement of the electric conductivity in the presence of a magnetic field, an important property of matter that has been studied for decades. It is conventionally associated with a magnetic-field-induced spin polarization, which drastically reduces spin scattering, thus electric resistance. Our earlier studies uncover an intriguing exception to this rule in that the electric resistivity in a magnetic insulator is reduced by up to 7 orders of magnitude only when a spin polarization is absent [1]. Here I report a newly identified quantum state in a honeycomb material where internal loop currents flowing along edges of crystal unit cells dictate electric conductivity, providing a key element driving the novel colossal magnetoresistance [2]. The unique nature and control of the exotic quantum state, along with implications of this discovery, will be presented and discussed after a brief review of conventional colossal magnetoresistance and loop currents in other materials.
References:
1. Colossal magnetoresistance via avoiding fully polarized magnetization in ferrimagnetic insulator Mn3Si2Te6, Yifei Ni, Hengdi Zhao, Yu Zhang, Bing Hu, Itamar Kimchi and Gang Cao, Letter of Phys. Rev. B 103, L161105 (2021); DOI:10.1103/PhysRevB.103.L161105
2. Control of chiral orbital currents in a colossal magnetoresistance material, Yu Zhang, Yifei Ni, Hengdi Zhao, Sami Hakani, Feng Ye, Lance DeLong, Itamar Kimchi, and Gang Cao, Nature, October 12, 2022, DOI: 10.1038/s41586-022-05262-3
YouTube Recording
Dr. Shmuel Nussinov, Professor Emeritus
School of Physics and Astronomy
Tel Aviv University
Tel Aviv, Israel
Research Profile
Abstract:
Aspects and the general outlay of the unique field of DM (dark matter) research will be highlighted. Some of the many types of DM as well as their interrelations, motivations by physics beyond the Standard Model, and ideas as how to search for them are described. This will be mainly done by focusing on DM made of black holes and of axions and axion-like particles. I will also note some DM types, which if realized in nature cannot be missed. On the other end of the "spectrum" of DM types, we have a case - related to the "Quirk" models of possible great technological interest - that only measurements of decaying black holes may indicate their existence.
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School of Physics and Astronomy
Tel Aviv University
Tel Aviv, Israel
Research Profile
Abstract:
Aspects and the general outlay of the unique field of DM (dark matter) research will be highlighted. Some of the many types of DM as well as their interrelations, motivations by physics beyond the Standard Model, and ideas as how to search for them are described. This will be mainly done by focusing on DM made of black holes and of axions and axion-like particles. I will also note some DM types, which if realized in nature cannot be missed. On the other end of the "spectrum" of DM types, we have a case - related to the "Quirk" models of possible great technological interest - that only measurements of decaying black holes may indicate their existence.
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Dr. Mariama Rebello de Sousa Dias, Assistant Professor
Department of Physics
University of Richmond
Richmond, VA
Research Profile
Abstract:
Using nanostructures with different chemical compositions and geometry is a promising way to improve the performance of optical sensors, energy harvesting devices, and photocatalysts. However, photonic materials for high-temperature applications must withstand their temperature operation while keeping their function.
In the first part of this talk, I will highlight recent progress in using alloys with different chemical compositions as a pathway to control and tune their optical response. In order to determine the ideal composition for a particular application, we use a combination of traditional methods of material synthesis and characterization and simulation and modeling methods. In particular, Au-Al shows to be promising for sensor applications operating at high temperatures. Here, we designed an artificial neural network trained to predict an Al-Au system's dielectric response. To confirm our prediction, we fabricated bimetallic films with different compositions and measured their optical response at different temperatures. We find that the accuracy of the ML is very high, and the time response is relatively short. Moreover, we show that all alloys outperform their pure counterparts in sensitivity, with Au0.85Al0.15 being the best candidate for replacing pure gold in sensors based on the surface plasmon resonance effect. This approach can expand optical properties databases of known and hypothetical systems.
In the second part, I will report the recent advancements in emitter design for thermophotovoltaics (TPVs). In thermophotovoltaics, heat from a thermal emitter is directly converted to electricity via a photovoltaic (PV) cell. One route to decrease losses in the system is to tailor the emitted spectrum to a specific PV cell. In this work, we propose to use a thin film configuration for the emitter. We define a figure of merit (FOM) as the ratio of the power generated by the photovoltaic cell () and the power emitted by the emitter (). We analyze the optimal configuration of >2000 emitters that can operate at temperatures above 2000 ºC. The methods implemented here apply to any PV cell. Thus, we evaluate the best emitter candidates for Si, Ge, GaSb, InGaAs, and InGaAsSb cells. Due to the ultra-high temperature operation of the thermophotovoltaic, the thermal stability and the mismatch in the thermal expansion coefficient of each material combination are discussed. Our results show that FOMs above 50% are achievable under ideal conditions. This work can shed light on high-temperature photonics, where a simple emitter design can result in higher efficient photoelectronic devices.
YouTube Recording
Department of Physics
University of Richmond
Richmond, VA
Research Profile
Abstract:
Using nanostructures with different chemical compositions and geometry is a promising way to improve the performance of optical sensors, energy harvesting devices, and photocatalysts. However, photonic materials for high-temperature applications must withstand their temperature operation while keeping their function.
In the first part of this talk, I will highlight recent progress in using alloys with different chemical compositions as a pathway to control and tune their optical response. In order to determine the ideal composition for a particular application, we use a combination of traditional methods of material synthesis and characterization and simulation and modeling methods. In particular, Au-Al shows to be promising for sensor applications operating at high temperatures. Here, we designed an artificial neural network trained to predict an Al-Au system's dielectric response. To confirm our prediction, we fabricated bimetallic films with different compositions and measured their optical response at different temperatures. We find that the accuracy of the ML is very high, and the time response is relatively short. Moreover, we show that all alloys outperform their pure counterparts in sensitivity, with Au0.85Al0.15 being the best candidate for replacing pure gold in sensors based on the surface plasmon resonance effect. This approach can expand optical properties databases of known and hypothetical systems.
In the second part, I will report the recent advancements in emitter design for thermophotovoltaics (TPVs). In thermophotovoltaics, heat from a thermal emitter is directly converted to electricity via a photovoltaic (PV) cell. One route to decrease losses in the system is to tailor the emitted spectrum to a specific PV cell. In this work, we propose to use a thin film configuration for the emitter. We define a figure of merit (FOM) as the ratio of the power generated by the photovoltaic cell () and the power emitted by the emitter (). We analyze the optimal configuration of >2000 emitters that can operate at temperatures above 2000 ºC. The methods implemented here apply to any PV cell. Thus, we evaluate the best emitter candidates for Si, Ge, GaSb, InGaAs, and InGaAsSb cells. Due to the ultra-high temperature operation of the thermophotovoltaic, the thermal stability and the mismatch in the thermal expansion coefficient of each material combination are discussed. Our results show that FOMs above 50% are achievable under ideal conditions. This work can shed light on high-temperature photonics, where a simple emitter design can result in higher efficient photoelectronic devices.
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Dr. Bob Bernstein, Scientist II
Fermi National Accelerator Facility
Batavia, IL
Research Profile
Abstract:
The Standard Model has three generations of quarks, three of charged leptons (the electron, muon, and tau), and three neutrinos (neutral leptons) corresponding to their charged companions. Quarks and neutrinos change flavor: quarks can change into other types of quarks, and neutrinos oscillate. Charged leptons seem unique: we do not see muons changing into electrons or any other mixing among them. We discuss an experiment under construction at Fermilab to search for muons changing into electrons at order 10^{-17}, an extraordinarily rare process probing mass scales up to 10,000 TeV. This colloquium will also show how basic physics we learn as undergraduates and graduate students is used every day in designing, constructing, and operating modern experiments.
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Fermi National Accelerator Facility
Batavia, IL
Research Profile
Abstract:
The Standard Model has three generations of quarks, three of charged leptons (the electron, muon, and tau), and three neutrinos (neutral leptons) corresponding to their charged companions. Quarks and neutrinos change flavor: quarks can change into other types of quarks, and neutrinos oscillate. Charged leptons seem unique: we do not see muons changing into electrons or any other mixing among them. We discuss an experiment under construction at Fermilab to search for muons changing into electrons at order 10^{-17}, an extraordinarily rare process probing mass scales up to 10,000 TeV. This colloquium will also show how basic physics we learn as undergraduates and graduate students is used every day in designing, constructing, and operating modern experiments.
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Paul Reimer, Research Scientist
Argonne National Laboratory
Lemont, IL
Research Profile
Abstract:
Argonne National Laboratory
Lemont, IL
Research Profile
Abstract:
The conventional picture of the proton is based on three “valence” quarks—two “up”
and one “down." This picture has done a remarkable job of describing many properties
of the proton. However, the richness of QCD reveals the proton as a much more complicated
object. In addition to the valence quarks, the proton contains a “sea” of quark-antiquark
pairs and gluons that bind the system together and are responsible for the majority
of the proton’s mass. Using the Drell-Yan process, a remarkable asymmetry has been
observed in the difference of anti-down to anti-up quarks in the proton. This asymmetry
cannot simply be generated through perturbative QCD, but rather indicates an underlying
and fundamental antiquark component in the proton. This talk will present the latest
results from the SeaQuest experiment on the flavor asymmetry in the proton sea, and
compare these results with previous measurements, phenomenological parton distributions
fits, and models of the proton.
This work is supported in part by the U.S. Department of Energy, Office of Nuclear
Physics, under Contract No. DE-AC02-06CH11357.
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Dr. Michael Dickson, Professor
Department of Philosophy
University of South Carolina
Columbia, SC
Research Profile
Abstract:
Since at least the 1950s, arguments based on various 'anthropic principles', and related arguments based on the apparently narrow range of physical parameters that allow for intelligent life, have persistently appeared and re-appeared in various sciences, especially cosmology. The arguments have proven very seductive, but they are based on two mistakes about the nature of scientific explanation, especially as regards modal propositions (propositions regarding possibility and necessity) and propositions about (allegedly) low-probably events.
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Department of Philosophy
University of South Carolina
Columbia, SC
Research Profile
Abstract:
Since at least the 1950s, arguments based on various 'anthropic principles', and related arguments based on the apparently narrow range of physical parameters that allow for intelligent life, have persistently appeared and re-appeared in various sciences, especially cosmology. The arguments have proven very seductive, but they are based on two mistakes about the nature of scientific explanation, especially as regards modal propositions (propositions regarding possibility and necessity) and propositions about (allegedly) low-probably events.
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Dr. Alexander Yankovsky, Professor
School of the Earth, Ocean, and Environment
University of South Carolina
Columbia, SC
Research Profile
Abstract:
River discharge running off into a coastal ocean with saltier (and hence denser) water produces buoyancy currents. Under the influence of the Earth’s rotation, buoyancy currents propagate along the coast. However, light wind can deflect the buoyancy current offshore as an elongated tongue of a relatively light water sometimes reaching the deep ocean 100-150 km away. In this situation, coastal buoyancy currents can act as important pathways for pollutants, nutrients and sediments originating inland. Surprisingly, these buoyancy currents don’t expand laterally in the manner of a smoke trail coming from a chimney, which makes them efficient contributors to the transport processes across submerged continental margins. Recent shipboard observations supplemented by idealized numerical modeling reveal complex dynamics governing the spreading of the buoyancy water offshore.
YouTube Recording
School of the Earth, Ocean, and Environment
University of South Carolina
Columbia, SC
Research Profile
Abstract:
River discharge running off into a coastal ocean with saltier (and hence denser) water produces buoyancy currents. Under the influence of the Earth’s rotation, buoyancy currents propagate along the coast. However, light wind can deflect the buoyancy current offshore as an elongated tongue of a relatively light water sometimes reaching the deep ocean 100-150 km away. In this situation, coastal buoyancy currents can act as important pathways for pollutants, nutrients and sediments originating inland. Surprisingly, these buoyancy currents don’t expand laterally in the manner of a smoke trail coming from a chimney, which makes them efficient contributors to the transport processes across submerged continental margins. Recent shipboard observations supplemented by idealized numerical modeling reveal complex dynamics governing the spreading of the buoyancy water offshore.
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Dr. Alexey Petrov, Professor and Endowed Chair
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
One of the conditions for creating a matter-dominated Universe is the presence of interactions that differentiate between matter and anti-matter. The properties of such interactions can be probed at particle accelerators by studying the decay patterns of produced particles. In recent years LHCb, one of the CERN's major experiments, announced the observation of CP-violation in the decays of particles containing charm quark. I discuss the theoretical implications of this important discovery and why it took experimentalists such a long time to make this observation. I will also discuss why it would take even longer for theorists to discern it.
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Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
One of the conditions for creating a matter-dominated Universe is the presence of interactions that differentiate between matter and anti-matter. The properties of such interactions can be probed at particle accelerators by studying the decay patterns of produced particles. In recent years LHCb, one of the CERN's major experiments, announced the observation of CP-violation in the decays of particles containing charm quark. I discuss the theoretical implications of this important discovery and why it took experimentalists such a long time to make this observation. I will also discuss why it would take even longer for theorists to discern it.
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Dr. Garrett Darl Lewis, Senior Physicist and Wargaming Principal Investigator
Directed Energy Directorate
Air Force Research Laboratory
Kirtland Air Force Base
Albuquerque, New Mexico
Research Profile
Directed Energy Directorate
Air Force Research Laboratory
Kirtland Air Force Base
Albuquerque, New Mexico
Research Profile
Abstract:
In recent years, directed energy (DE) technology has advanced to the cusp of the battlefield and beyond. With several recent examples of DE being employed in combat, this presentation will address questions relating to the military applications of DE, including the who, what, where, when, and why of DE weapons. It will focus on the unique challenges and opportunities associated with developing DE in the lab, identifying the appropriate applications, and transitioning the resulting product to the field.
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In recent years, directed energy (DE) technology has advanced to the cusp of the battlefield and beyond. With several recent examples of DE being employed in combat, this presentation will address questions relating to the military applications of DE, including the who, what, where, when, and why of DE weapons. It will focus on the unique challenges and opportunities associated with developing DE in the lab, identifying the appropriate applications, and transitioning the resulting product to the field.
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Dr. Varsha Kulkarni, Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The James Webb Space Telescope (JWST), launched on Dec. 25, 2021, is the successor to the Hubble Space Telescope (HST). The JWST is designed to observe primarily in the infrared and is expected to be far more powerful than HST or other past space telescopes for observations of a variety of astronomical objects, such as extrasolar planets and very distant galaxies. We have been approved to use JWST's mid-infrared instrument to study interstellar dust grains in distant galaxies. I will review some of the unique features of the JWST, its expected benefits over the HST, and its current status. I will also describe our planned observations of distant dusty galaxies with JWST and the motivations for these studies to understand the impact of dust on the physics and chemistry of the interstellar medium and on the appearance of the distant universe.
The James Webb Space Telescope (JWST), launched on Dec. 25, 2021, is the successor to the Hubble Space Telescope (HST). The JWST is designed to observe primarily in the infrared and is expected to be far more powerful than HST or other past space telescopes for observations of a variety of astronomical objects, such as extrasolar planets and very distant galaxies. We have been approved to use JWST's mid-infrared instrument to study interstellar dust grains in distant galaxies. I will review some of the unique features of the JWST, its expected benefits over the HST, and its current status. I will also describe our planned observations of distant dusty galaxies with JWST and the motivations for these studies to understand the impact of dust on the physics and chemistry of the interstellar medium and on the appearance of the distant universe.
Dr. Revaz Ramazashvili, Research Scientist
Laboratoire de Physique Théorique
Université Paul Sabatier
Toulouse, France
Research Profile
Dr. Ramazashvili is also a visiting professor at the University of South Carolina during the Spring 2022 term as part of the McCausland Visiting Scholars Program (College of Arts and Sciences).
Laboratoire de Physique Théorique
Université Paul Sabatier
Toulouse, France
Research Profile
Dr. Ramazashvili is also a visiting professor at the University of South Carolina during the Spring 2022 term as part of the McCausland Visiting Scholars Program (College of Arts and Sciences).
Abstract:
We show that, in a Néel antiferromagnet with a particular location of electron band extrema, a Skyrmion and an electron form a bound state with energy of the order of the gap $\Delta$ in the electron spectrum. The bound state turns the Skyrmion into a charged particle that can be manipulated by electric field. We identify a region in the space of coupling constants, where the Skyrmion-electron bound state makes the (otherwise metastable) Skyrmion genuinely stable.
Reference: arXiv 2203.03569
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We show that, in a Néel antiferromagnet with a particular location of electron band extrema, a Skyrmion and an electron form a bound state with energy of the order of the gap $\Delta$ in the electron spectrum. The bound state turns the Skyrmion into a charged particle that can be manipulated by electric field. We identify a region in the space of coupling constants, where the Skyrmion-electron bound state makes the (otherwise metastable) Skyrmion genuinely stable.
Reference: arXiv 2203.03569
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Dr. Céline Péroux, ANDES Project Scientist (Involvement at Extremely Large Telescope)
European Southern Observatory
München, Germany
Research Profile
European Southern Observatory
München, Germany
Research Profile
Abstract:
These are incredibly exciting times for extra-galactic astrophysics; above all for studies of galaxy formation and growth of structure. New observatories and advanced simulations are revolutionizing our understanding of the cycling of matter into, through, and out of galaxies. In this talk, I will provide an overview of the normal matter in collapsed structures, their chemical make-up and dust content. I
These are incredibly exciting times for extra-galactic astrophysics; above all for studies of galaxy formation and growth of structure. New observatories and advanced simulations are revolutionizing our understanding of the cycling of matter into, through, and out of galaxies. In this talk, I will provide an overview of the normal matter in collapsed structures, their chemical make-up and dust content. I
will present fresh clues of the cosmic evolution of cold gas; revisit the 20-year
old "missing metals problem" and introduce new calculations of the dust content of
the Universe up to early times. Together, these results provide an increasingly accurate
description of the baryon cycle, which plays many crucial roles in transforming the
bare pristine Universe left after the Big Bang into the rich and diverse Universe
in which we live today.
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Dr. Alexey Petrov, Professor
Department of Physics and Astronomy
College of Liberal Arts and Sciences
Wayne State University
Detroit, Michigan
Research Profile
Abstract:
Indirect searches for New Physics are the searches for quantum effects of new particles that can be discovered by observing tiny deviations between theoretical predictions and experimental observations.
I will discuss how physicists have been using bound muons to probe New Physics that is not reachable by direct searches at the Large Hadron Collider.
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Department of Physics and Astronomy
College of Liberal Arts and Sciences
Wayne State University
Detroit, Michigan
Research Profile
Abstract:
Indirect searches for New Physics are the searches for quantum effects of new particles that can be discovered by observing tiny deviations between theoretical predictions and experimental observations.
I will discuss how physicists have been using bound muons to probe New Physics that is not reachable by direct searches at the Large Hadron Collider.
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Dr. Mu Wang, Editor of Physical Review Materials
The Editorial Office
American Physical Society
Ridge, New York
National Laboratory of Solid State Microstructures and Department of Physics
Nanjing University
Nanjing, China
Research Profile
Abstract:
Optics on the nanoscale is a fast developing area with many exciting novel concepts, phenomena, and functionalities. Unexpected effects in the early days can be realized now by designing subwavelength structures judiciously.
In this lecture, I will focus on some fundamentals of nanophotonics as well as introduce some new concepts and structures that lead to novel functionalities. I will also discuss designing a single piece of metasurface that simultaneously generates different polarization states for multichannel distribution and transformation of entangled photon states.
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The Editorial Office
American Physical Society
Ridge, New York
National Laboratory of Solid State Microstructures and Department of Physics
Nanjing University
Nanjing, China
Research Profile
Abstract:
Optics on the nanoscale is a fast developing area with many exciting novel concepts, phenomena, and functionalities. Unexpected effects in the early days can be realized now by designing subwavelength structures judiciously.
In this lecture, I will focus on some fundamentals of nanophotonics as well as introduce some new concepts and structures that lead to novel functionalities. I will also discuss designing a single piece of metasurface that simultaneously generates different polarization states for multichannel distribution and transformation of entangled photon states.
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Dr. Qi An, Assistant Professor
Department of Chemical and Materials Engineering
College of Engineering
University of Nevada, Reno
Reno, Nevada
Abstract:
Overconsumption of fuel oils and the resulting energy crisis have been increasingly causing environmental issues such as global climate change and marine pollution. Solid-state thermoelectric (TE) technology, enabling direct conversion between heat and electricity without moving parts, offers the possibility of relieving the current energy crisis. The widespread application of TE technology requires TE materials with high conversion efficiency and robust mechanical properties. However, it has been challenging to develop highly stable and efficient TE materials in cost and time-consuming experiments. Computer simulations may dramatically accelerate the design of novel TE materials with desirable properties.
In this talk, we illustrate how to improve the mechanical properties and efficiency of TE materials via microstructure engineering and light irradiation via an AI-based theoretical framework including machine learning, quantum mechanics, and atomistic simulations. First, we show that the strength of Bi2Te3 can be significantly enhanced due to the nanoscale twins. For Bi2Te3, the strengthening mechanism is due to the formation of twin boundaries between the Te atoms of adjacent Te1─Bi─Te2─Bi─Te1 quint substructures. Then we show that sphalerite ZnS transforms from a dislocation dominated deformation mode in the ground state to a twin dominated deformation mode with bandgap electronic excitations, leading to increased strength and brittle failure under light illumination. Next, we show that the lattice thermal conductivity (LTC) of Mg2Si can be significantly reduced due to the nanoscale twins, which increases the conversion efficiency between heat and electricity. The soft Mg-Mg bond formed along TBs leads to soft acoustic and optical modes, shorter phonon lifetimes, and higher phonon scattering rates. Finally, we report the decreased LTC of high temperature TE material boron subphosphide (B12P2) by introducing the nanoscale twins. The decrease of vibrational density of states and phonon participation ratio due to TBs' phonon scattering is the main reason for the low LTC in nanotwinned B12P2. The new knowledge gained in this talk is important for the future design of novel TE materials with designed properties via controlling microstructures and light irradiation.
YouTube Recording
Department of Chemical and Materials Engineering
College of Engineering
University of Nevada, Reno
Reno, Nevada
Abstract:
Overconsumption of fuel oils and the resulting energy crisis have been increasingly causing environmental issues such as global climate change and marine pollution. Solid-state thermoelectric (TE) technology, enabling direct conversion between heat and electricity without moving parts, offers the possibility of relieving the current energy crisis. The widespread application of TE technology requires TE materials with high conversion efficiency and robust mechanical properties. However, it has been challenging to develop highly stable and efficient TE materials in cost and time-consuming experiments. Computer simulations may dramatically accelerate the design of novel TE materials with desirable properties.
In this talk, we illustrate how to improve the mechanical properties and efficiency of TE materials via microstructure engineering and light irradiation via an AI-based theoretical framework including machine learning, quantum mechanics, and atomistic simulations. First, we show that the strength of Bi2Te3 can be significantly enhanced due to the nanoscale twins. For Bi2Te3, the strengthening mechanism is due to the formation of twin boundaries between the Te atoms of adjacent Te1─Bi─Te2─Bi─Te1 quint substructures. Then we show that sphalerite ZnS transforms from a dislocation dominated deformation mode in the ground state to a twin dominated deformation mode with bandgap electronic excitations, leading to increased strength and brittle failure under light illumination. Next, we show that the lattice thermal conductivity (LTC) of Mg2Si can be significantly reduced due to the nanoscale twins, which increases the conversion efficiency between heat and electricity. The soft Mg-Mg bond formed along TBs leads to soft acoustic and optical modes, shorter phonon lifetimes, and higher phonon scattering rates. Finally, we report the decreased LTC of high temperature TE material boron subphosphide (B12P2) by introducing the nanoscale twins. The decrease of vibrational density of states and phonon participation ratio due to TBs' phonon scattering is the main reason for the low LTC in nanotwinned B12P2. The new knowledge gained in this talk is important for the future design of novel TE materials with designed properties via controlling microstructures and light irradiation.
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Dr. Sai Mu, Postdoctoral Fellow
Materials Department
College of Engineering
University of California, Santa Barbara
Santa Barbara, California
Research Profile
Abstract:
Today, disordered materials are commercially ubiquitous and underpin virtually all advanced technologies – energy, transportation, construction, communication, medicine. The recently discovered transition metal high entropy alloys (HEAs), and their cousin's general multicomponent concentrated solid solution alloys (CSAs) exhibit many exceptional and beneficial functionalities, opening a new paradigm for material design using extreme disorder. Given that all functionalities originate from the disorder-controlled fundamental physical properties, understanding how disorder influences the underlying electronic, vibrational and magnetic properties of transition metal compounds is crucial and this is the subject of the talk.
I will discuss two main topics. In the first topic, I will investigate the effect of disorder on energy dissipations in HEAs and CSAs through the electron and phonon degrees of freedom. I delineate different electron scattering mechanisms and identify the dominant electron scattering mechanisms giving rise to a two orders of magnitude resistivity difference observed in alloys containing combinations of closely related elements Ni, Co, Fe, Mn, and Cr. Disorder effect on lattice vibrations is also assessed, and the importance of heretofore overlooked force constant disorder in the phonon scattering is revealed. In the second topic, I will exploit disorder to increase the magnetic coupling and magnetic critical temperature, and also to tune the magnetic anisotropy of transition metal antiferromagnet Cr2O3. This leads to improved functionalities for spintronic applications. The disorder physics disclosed here has broad implications for materials design towards targeted properties – such as energy dissipation, magnetic properties – based on the exploitation of disorder.
YouTube Recording
Materials Department
College of Engineering
University of California, Santa Barbara
Santa Barbara, California
Research Profile
Abstract:
Today, disordered materials are commercially ubiquitous and underpin virtually all advanced technologies – energy, transportation, construction, communication, medicine. The recently discovered transition metal high entropy alloys (HEAs), and their cousin's general multicomponent concentrated solid solution alloys (CSAs) exhibit many exceptional and beneficial functionalities, opening a new paradigm for material design using extreme disorder. Given that all functionalities originate from the disorder-controlled fundamental physical properties, understanding how disorder influences the underlying electronic, vibrational and magnetic properties of transition metal compounds is crucial and this is the subject of the talk.
I will discuss two main topics. In the first topic, I will investigate the effect of disorder on energy dissipations in HEAs and CSAs through the electron and phonon degrees of freedom. I delineate different electron scattering mechanisms and identify the dominant electron scattering mechanisms giving rise to a two orders of magnitude resistivity difference observed in alloys containing combinations of closely related elements Ni, Co, Fe, Mn, and Cr. Disorder effect on lattice vibrations is also assessed, and the importance of heretofore overlooked force constant disorder in the phonon scattering is revealed. In the second topic, I will exploit disorder to increase the magnetic coupling and magnetic critical temperature, and also to tune the magnetic anisotropy of transition metal antiferromagnet Cr2O3. This leads to improved functionalities for spintronic applications. The disorder physics disclosed here has broad implications for materials design towards targeted properties – such as energy dissipation, magnetic properties – based on the exploitation of disorder.
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Dr. Oliviero Andreussi, Assistant Professor
Department of Physics
University of North Texas
Denton, Texas
Abstract:
Recent advances in computational models of solvent and electrolyte environments have opened the possibility of characterizing heterogeneous catalysis and electrochemistry in a first-principles-based framework, where the multiscale nature of the developed approaches provides a significant reduction of the computational burden while retaining a good accuracy. Here, the core methodological aspects and features of these recently developed approaches, as implemented in the ENVIRON library (www.quantum-environ.org), will be reviewed. Applications to the screenings of two-dimensional materials as electrocatalysts for the hydrogen evolution reaction (HER) and for the oxygen evolution and reduction reactions (OER and ORR) will be presented. The proposed screening workflows allowed us to identify promising materials with low thermodynamic overpotentials and significant stability under electrochemical conditions.
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Department of Physics
University of North Texas
Denton, Texas
Abstract:
Recent advances in computational models of solvent and electrolyte environments have opened the possibility of characterizing heterogeneous catalysis and electrochemistry in a first-principles-based framework, where the multiscale nature of the developed approaches provides a significant reduction of the computational burden while retaining a good accuracy. Here, the core methodological aspects and features of these recently developed approaches, as implemented in the ENVIRON library (www.quantum-environ.org), will be reviewed. Applications to the screenings of two-dimensional materials as electrocatalysts for the hydrogen evolution reaction (HER) and for the oxygen evolution and reduction reactions (OER and ORR) will be presented. The proposed screening workflows allowed us to identify promising materials with low thermodynamic overpotentials and significant stability under electrochemical conditions.
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Dr. Marc Dvorak, Research Fellow
Department of Applied Physics
Aalto University
Espoo, Finland
Research Profile
Abstract:
Electronic structure theory is concerned with predicting the energy levels and spectra of systems from first principles. The major challenge for the field is that electrons interact with each other, giving rise to properties like carrier lifetimes, magnetism, Kondo physics, and Mott insulators. I will introduce three approaches to the correlated electron problem: density functional theory, many-body Green's functions, and many-body wave functions, and draw special attention to the strengths and weaknesses of each. I will survey my own research in these three subjects covering III-V semiconductors, two-dimensional materials, and molecular dimers.
In the second half of the talk, I will focus on my current work developing a quantum embedding theory for strongly-correlated electrons, a regime in which typical electronic structure methods fail. The method keeps an exact many-body description for the wave function in an active space and relies on a quasiparticle renormalization of the Hamiltonian in the remaining portion of the Hilbert space. I will share initial results for dimers and porphyrins which are in good agreement with high quality reference data at lower computational cost. Finally, I will outline my long-term plans to extend the theory to solids in order to develop a robust, universal computational infrastructure for correlated phenomena with special emphasis on an ab-initio description of Kondo physics in designer interfaces.
YouTube Recording
Department of Applied Physics
Aalto University
Espoo, Finland
Research Profile
Abstract:
Electronic structure theory is concerned with predicting the energy levels and spectra of systems from first principles. The major challenge for the field is that electrons interact with each other, giving rise to properties like carrier lifetimes, magnetism, Kondo physics, and Mott insulators. I will introduce three approaches to the correlated electron problem: density functional theory, many-body Green's functions, and many-body wave functions, and draw special attention to the strengths and weaknesses of each. I will survey my own research in these three subjects covering III-V semiconductors, two-dimensional materials, and molecular dimers.
In the second half of the talk, I will focus on my current work developing a quantum embedding theory for strongly-correlated electrons, a regime in which typical electronic structure methods fail. The method keeps an exact many-body description for the wave function in an active space and relies on a quasiparticle renormalization of the Hamiltonian in the remaining portion of the Hilbert space. I will share initial results for dimers and porphyrins which are in good agreement with high quality reference data at lower computational cost. Finally, I will outline my long-term plans to extend the theory to solids in order to develop a robust, universal computational infrastructure for correlated phenomena with special emphasis on an ab-initio description of Kondo physics in designer interfaces.
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Dr. Matthias Schindler, Associate Professor and Director of Graduate Studies
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
In electromagnetism, there is a single charge that can take positive or negative values. An analogous quantity, called color, exists in the theory of the strong interactions, quantum chromodynamics (QCD). However, unlike the single electric charge, there are three color charges. This is one of the reasons why QCD is fairly intractable when it comes to nuclear physics. Improving our understanding of how this theory governs the interactions among protons and neutrons remains one of the main goals of nuclear physics. We can make progress towards this goal by considering a theory with not three, but a very large number of color charges. While it might seem strange that such a theory can tell us something useful about the world we live in, I will describe which features of the nuclear interactions can be understood from this approach and how it can be used in prioritizing future experiments searching for new physics.
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
In electromagnetism, there is a single charge that can take positive or negative values. An analogous quantity, called color, exists in the theory of the strong interactions, quantum chromodynamics (QCD). However, unlike the single electric charge, there are three color charges. This is one of the reasons why QCD is fairly intractable when it comes to nuclear physics. Improving our understanding of how this theory governs the interactions among protons and neutrons remains one of the main goals of nuclear physics. We can make progress towards this goal by considering a theory with not three, but a very large number of color charges. While it might seem strange that such a theory can tell us something useful about the world we live in, I will describe which features of the nuclear interactions can be understood from this approach and how it can be used in prioritizing future experiments searching for new physics.
Dr. Jeffrey Hazboun, Postdoctoral Research Associate
NANOGrav Physics Frontiers Center
Physical Sciences Division
University of Washington Bothell
Bothell, Washington
Research Profile
Abstract:
Pulsar timing arrays open a new band of the gravitational wave spectrum by building a galactic-scale GW detector. They will detect a stochastic background of gravitational waves in the next few years. The strongest signal is expected to be the unresolvable background from supermassive black hole binaries at the centers of merged galaxies. While SMBBHs are expected to be the strongest source of GWs, we are sensitive to any GW signal in the nanohertz regime. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is an NSF funded Physics Frontiers Center monitoring over 70 millisecond pulsars for the signature of these gravitational waves. In the NANOGrav 12.5-year dataset, we are seeing significant evidence for a signal in our data that is common among many of the pulsars. We currently find no definitive evidence for the correlated pattern that is indicative of gravitational waves. However, if we are seeing the first signs of the GW background, our models show that continued observations will lead to a detection within the next few years.
YouTube Recording
NANOGrav Physics Frontiers Center
Physical Sciences Division
University of Washington Bothell
Bothell, Washington
Research Profile
Abstract:
Pulsar timing arrays open a new band of the gravitational wave spectrum by building a galactic-scale GW detector. They will detect a stochastic background of gravitational waves in the next few years. The strongest signal is expected to be the unresolvable background from supermassive black hole binaries at the centers of merged galaxies. While SMBBHs are expected to be the strongest source of GWs, we are sensitive to any GW signal in the nanohertz regime. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is an NSF funded Physics Frontiers Center monitoring over 70 millisecond pulsars for the signature of these gravitational waves. In the NANOGrav 12.5-year dataset, we are seeing significant evidence for a signal in our data that is common among many of the pulsars. We currently find no definitive evidence for the correlated pattern that is indicative of gravitational waves. However, if we are seeing the first signs of the GW background, our models show that continued observations will lead to a detection within the next few years.
YouTube Recording
Dr. David Ceperley, Founder Professor of Physics
Department of Physics
University of Illinois at Urbana-Champaign
Champaign, Illinois
Research Profile
Abstract:
Dense hydrogen is the most common constituent of the universe forming the majority of the giant planets, Jupiter and Saturn, as well as the extra solar planets. Hydrogen, though the simplest atom, becomes complex under extreme conditions of pressure. Hydrogen is an ideal test platform for ab initio simulation techniques. Using these methods, we predicted that hydrogen transforms from a molecular liquid to an atomic liquid via a first order transition. This was later verified in experiment. In 1965, Neil Ashcroft predicted that high pressure metallic hydrogen will be a high superconductor at room temperature. Recently, hydrides such at LaH10 were predicted and then found to be superconducting at elevated temperatures. Machine learning techniques have recently been used to make new predictions about the hydrogen phase diagram.
YouTube Recording
Department of Physics
University of Illinois at Urbana-Champaign
Champaign, Illinois
Research Profile
Abstract:
Dense hydrogen is the most common constituent of the universe forming the majority of the giant planets, Jupiter and Saturn, as well as the extra solar planets. Hydrogen, though the simplest atom, becomes complex under extreme conditions of pressure. Hydrogen is an ideal test platform for ab initio simulation techniques. Using these methods, we predicted that hydrogen transforms from a molecular liquid to an atomic liquid via a first order transition. This was later verified in experiment. In 1965, Neil Ashcroft predicted that high pressure metallic hydrogen will be a high superconductor at room temperature. Recently, hydrides such at LaH10 were predicted and then found to be superconducting at elevated temperatures. Machine learning techniques have recently been used to make new predictions about the hydrogen phase diagram.
YouTube Recording
Mr. Travis Dore, PhD Student
Department of Physics
University of Illinois at Urbana-Champaign
Champaign, Illinois
Abstract:
Microseconds after the Big Bang, the Universe was filled with strongly interacting matter called the quark gluon plasma. In the lab, we recreate these settings by colliding together heavy nuclei at extremely large energies. This leads to the largest temperatures ever produced in a lab as well as the production of the quark gluon plasma. The subsequent evolution after collision can be modelled hydrodynamically, which has done extremely well at both describing and predicting data.
In this talk, I will go through the history leading up to the first heavy ion collisions and the discovery of the deconfinement transition as well as give an overview of the current state of the field. I will focus specifically on the hydrodynamic evolution and out-of-equilibrium effects on the search for the critical point of the deconfinement transition.
YouTube Recording
Department of Physics
University of Illinois at Urbana-Champaign
Champaign, Illinois
Abstract:
Microseconds after the Big Bang, the Universe was filled with strongly interacting matter called the quark gluon plasma. In the lab, we recreate these settings by colliding together heavy nuclei at extremely large energies. This leads to the largest temperatures ever produced in a lab as well as the production of the quark gluon plasma. The subsequent evolution after collision can be modelled hydrodynamically, which has done extremely well at both describing and predicting data.
In this talk, I will go through the history leading up to the first heavy ion collisions and the discovery of the deconfinement transition as well as give an overview of the current state of the field. I will focus specifically on the hydrodynamic evolution and out-of-equilibrium effects on the search for the critical point of the deconfinement transition.
YouTube Recording
Dr. Frank T. Avignone, III, Carolina Endowed Professor of Physics and Astronomy
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
Neutrino-less nuclear double-beta decay is the only practical way to determine if
neutrinos are their own anti particles, Majorana particles. The direct observation
of this process would be the first observation of the violation of the important symmetry, the conservation of lepton number. The measurement of the half life of this decay, combined with neutrino-oscillation data, would determine the mass scale of neutrinos. It is clear that such a discovery would have great impact on nuclear physics, particle physics, astrophysics, and cosmology.
The CUORE experiment in the Gran Sasso Underground Laboratory in Assergi, Italy has just completed collecting a ton-year of exposure with an important null result. The next generation experiment, CUPID (CUORE with Particle Identification) has just been approved for funding by both DOE and the NSF. Five UofSC faculty and ten of our departmental graduate students have worked on CUORE's development, construction, operation, and data analysis. A brief introduction of the theoretical
issues will be followed by a description of the experiment, the results, and a brief discussion of the future experiment, CUPID.
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Dr. Jerome Goldstein, Professor
Department of Mathematical Sciences
University of Memphis
Memphis, Tennessee
Research Profile
Abstract:
A. Einstein and (others) in 1905 derived Brownian motion from a random walk and the central limit theorem of statistics, and this derivation led to the first numerical estimate for Avogadro’s number. In 1920, G. I. Taylor used a different random walk to derive the telegraph equation, a different approach to diffusion, and it was related to the Poisson process. In 1930, L. Ornstein and G. Uhlenbeck (the “inventor” of electron spin) derived a different approach to diffusion, which was rejected by the physicists and embraced by the mathematicians. This led to many subsequent results, still in the process of development. We’ll try to fit this all together.
YouTube Recording
Department of Mathematical Sciences
University of Memphis
Memphis, Tennessee
Research Profile
Abstract:
A. Einstein and (others) in 1905 derived Brownian motion from a random walk and the central limit theorem of statistics, and this derivation led to the first numerical estimate for Avogadro’s number. In 1920, G. I. Taylor used a different random walk to derive the telegraph equation, a different approach to diffusion, and it was related to the Poisson process. In 1930, L. Ornstein and G. Uhlenbeck (the “inventor” of electron spin) derived a different approach to diffusion, which was rejected by the physicists and embraced by the mathematicians. This led to many subsequent results, still in the process of development. We’ll try to fit this all together.
YouTube Recording
Dr. Robert Cava
Russell Wellman Moore Professor of Chemistry
Department of Chemistry
Princeton University
Princeton, New Jersey
Research Profile
Abstract:
Finding new materials that are of interest in the community of materials physicists is, in my view, best done by using the insights and tools of solid state chemistry to direct exploratory synthesis towards finding materials with potentially new electronic and magnetic properties. Unfortunately, however, most solid state chemists do not feel comfortable with the language of physics, and further compounding the disconnect between physics and chemistry, materials physicists do not in general understand the complexities of chemistry and its language. Theoretical physicists, who I personally find to be lots of fun, seem even further in research culture from “bench chemists”, making chemical research even harder to aim towards forefront physics though it is the theorists who most often live in gardens of untested ideas.
In this talk, I plan to describe materials in several different chemical families that we have worked on in recent years - found from a distinctly chemical perspective, I think, with their potential significance to materials physics in mind. Some of them you may find interesting and others not so interesting. The main idea is to keep trying, propose and find new materials to see what sticks, welcome collaborations, and never give up.
YouTube Recording
Russell Wellman Moore Professor of Chemistry
Department of Chemistry
Princeton University
Princeton, New Jersey
Research Profile
Abstract:
Finding new materials that are of interest in the community of materials physicists is, in my view, best done by using the insights and tools of solid state chemistry to direct exploratory synthesis towards finding materials with potentially new electronic and magnetic properties. Unfortunately, however, most solid state chemists do not feel comfortable with the language of physics, and further compounding the disconnect between physics and chemistry, materials physicists do not in general understand the complexities of chemistry and its language. Theoretical physicists, who I personally find to be lots of fun, seem even further in research culture from “bench chemists”, making chemical research even harder to aim towards forefront physics though it is the theorists who most often live in gardens of untested ideas.
In this talk, I plan to describe materials in several different chemical families that we have worked on in recent years - found from a distinctly chemical perspective, I think, with their potential significance to materials physics in mind. Some of them you may find interesting and others not so interesting. The main idea is to keep trying, propose and find new materials to see what sticks, welcome collaborations, and never give up.
YouTube Recording
Dr. Michael Susner
Research Materials Engineer (DR-02)
Materials and Manufacturing Directorate
RXAPE, Photonics Branch
The Air Force Research Laboratory
Wright-Patterson Air Force Base
Wright-Patterson Air Force Base, Ohio
Research Profile
Abstract:
Correlated two-dimensional (2D) materials offer a new avenue for the development of next-generation electronic devices. Since the discovery of Dirac physics in graphene, research in 2D materials has grown exponentially with two main aims: 1) the discovery of new 2D materials and 2) developing new and innovative techniques to harness and tune their optical, magnetic, and electronic properties. This talk will cover 2D materials in general with a focus on Van der Waals bonding, band structure, magnetism, and other correlated electron behavior and the manipulation of these properties via reduced dimensionality. A few prominent cases will be highlighted.
Though most research on 2D materials has focused on graphene, boron nitride, and transition metal chalcogenides (TMCs),1,2 new 2D materials classes are coming into the forefront, including metal thiophosphates3 which, in many ways, are the 2D equivalent of complex oxides as changes in composition, stacking, or pressure in turn lead to large changes in bandgap4, magnetic ordering temperature and type3, ferroelectric ordering temperature3,5, possible Kitaev physics6 (i.e. quantum spin liquids) and even the appearance of superconductivity.7 I shall present the materials characterization of CuInP2S6 and related self-assembled CuInP2S6/In4/3P2S6 heterostructures as a case study for this materials class in particular and 2D materials in general to show how the underlying physics is affected by chemical and structural modifications.
Research Materials Engineer (DR-02)
Materials and Manufacturing Directorate
RXAPE, Photonics Branch
The Air Force Research Laboratory
Wright-Patterson Air Force Base
Wright-Patterson Air Force Base, Ohio
Research Profile
Abstract:
Correlated two-dimensional (2D) materials offer a new avenue for the development of next-generation electronic devices. Since the discovery of Dirac physics in graphene, research in 2D materials has grown exponentially with two main aims: 1) the discovery of new 2D materials and 2) developing new and innovative techniques to harness and tune their optical, magnetic, and electronic properties. This talk will cover 2D materials in general with a focus on Van der Waals bonding, band structure, magnetism, and other correlated electron behavior and the manipulation of these properties via reduced dimensionality. A few prominent cases will be highlighted.
Though most research on 2D materials has focused on graphene, boron nitride, and transition metal chalcogenides (TMCs),1,2 new 2D materials classes are coming into the forefront, including metal thiophosphates3 which, in many ways, are the 2D equivalent of complex oxides as changes in composition, stacking, or pressure in turn lead to large changes in bandgap4, magnetic ordering temperature and type3, ferroelectric ordering temperature3,5, possible Kitaev physics6 (i.e. quantum spin liquids) and even the appearance of superconductivity.7 I shall present the materials characterization of CuInP2S6 and related self-assembled CuInP2S6/In4/3P2S6 heterostructures as a case study for this materials class in particular and 2D materials in general to show how the underlying physics is affected by chemical and structural modifications.
1. Chhowalla, M. et al. The chemistry of two-dimensional layered transition metal
dichalcogenide nanosheets. Nat. Chem. 5, 263–275 (2013).
2. Schaibley, J. R. et al. Valleytronics in 2D materials. Nat. Rev. Mater. 1, 1–15 (2016).
3. Susner, M. A., Chyasnavichyus, M., McGuire, M. A., Ganesh, P. & Maksymovych, P.
Metal Thio- and Selenophosphates as Multifunctional van der Waals Layered Materials.
Adv. Mater. 29, 1602852 (2017).
4. Wang, F. et al. 2D library beyond graphene and transition metal dichalcogenides:
a focus on photodetection. Chem. Soc. Rev. 47, 6296–6341 (2018).
5. Susner, M. A. et al. High TC layered Ferrielectric Crystals by Coherent Spinodal Decomposition. ACS Nano 9, 12365–12373 (2015).
6. Kim, C. et al. Spin waves in the two-dimensional honeycomb lattice XXZ-type van
der Waals antiferromagnet CoPS3. Phys. Rev. B 102, (2020).
7. Wang, Y. et al. Emergent superconductivity in an iron-based honeycomb lattice
initiated by pressure-driven spin-crossover. Nat. Commun. 9, (2018).
Dr. James Tour
T.T. and W.F. Chao Professor of Chemistry
Professor of Materials Science and NanoEngineering
Department of Chemistry
Wiess School of Natural Sciences
Rice University
Houston, Texas
Research Profile
Abstract:
A method will be described for making graphene in 10 milliseconds from any solid carbon source using no solvents, no water, and only $35 per ton in electricity. The sources include coal, petroleum coke, food, and mixed waste plastic. Application of this method to the formation of metal carbides and other 2D materials will also be shown.
YouTube Recording
T.T. and W.F. Chao Professor of Chemistry
Professor of Materials Science and NanoEngineering
Department of Chemistry
Wiess School of Natural Sciences
Rice University
Houston, Texas
Research Profile
Abstract:
A method will be described for making graphene in 10 milliseconds from any solid carbon source using no solvents, no water, and only $35 per ton in electricity. The sources include coal, petroleum coke, food, and mixed waste plastic. Application of this method to the formation of metal carbides and other 2D materials will also be shown.
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Dr. Hariharan Srikanth, Distinguished University Professor
Department of Physics
College of Arts and Sciences
University of South Florida
Tampa, Florida
Research Profile
Abstract:
Department of Physics
College of Arts and Sciences
University of South Florida
Tampa, Florida
Research Profile
Abstract:
Magnetic nanoparticles have been building blocks in applications ranging from high
density recording to spintronics and nanomedicine. Magnetic anisotropies in nanoparticles arising from surfaces, shapes, and interfaces
in hybrid structures are important in determining the functional response in various
applications. In this talk, I will first introduce the basic aspects of effective
anisotropy and measurements through RF transverse susceptibility experiments. Tuning magnetic anisotropy has a direct impact on the performance of functional magnetic
nanoparticles in biomedical applications such as enhanced MRI contrast and magnetic
hyperthermia cancer therapy [1]. There is a need to improve the surface functionalization
and specific absorption rate (SAR) or heating efficiency of nanoparticles for cancer
diagnostics and therapy. Strategies going beyond simple spherical structures, such
as exchange coupled core-shell nanoparticles, nanowire, and nanotube geometries can
be exploited to increase saturation magnetization, effective anisotropy, and heating
efficiency in magnetic hyperthermia. This talk will combine insights into fundamental
physics of magnetic nanostructures along with recent research advances in their application
in cancer therapy and diagnostics in nanomedicine.
1] “Hybrid magnetic nanoparticles as efficient nanoheaters in biomedical applications”
(mini-review) - G.C. Lavorato, R. Das, J. Alonso Masa, M.H. Phan and H. Srikanth, Nanoscale Advances 3, 867 (2021)
Dr. Rongying Jin, Professor
Department of Physics and Astronomy
College of Science
Louisiana State University
Baton Rouge, Louisiana
Abstract:
Department of Physics and Astronomy
College of Science
Louisiana State University
Baton Rouge, Louisiana
Abstract:
The discovery of nontrivial topological properties in condensed matter started a new
era of physics. Many fermionic particles predicted in high-energy physics are now
experimentally realized in topological materials such as Dirac, Weyl, and Majorana
particles. Their nontrivial topology results from crossings of conduction and valence
bands. Depending on crystal symmetry, such crossings can result in degeneracy (g)
with g = 2, 3, 4, 6, and 8. It is known that g = 2 corresponds to Weyl fermions and
g = 4 corresponds to Dirac fermions. The cases of g = 3, 6, and 8 are particularly
interesting as they can only be found in condensed matter systems, having no high
energy analogues as constrained by crystal symmetry.
In this talk, I will present examples such as BaMnSb2 (g = 2), PtBi2 (g = 3), TaSe3 (g = 4) and PdSb2 (g = 6). By analyzing quantum oscillations observed in these compounds, we obtain
topological properties of the bands. The interaction between topology and physics has been a triumph over the past decade
and is exploding into the disciplines of quantum science and technology.
Dr. Luis Balicas, Professor and Research Faculty Member
Department of Physics
College of Arts and Sciences
Florida State University
National High Magnetic Field Laboratory (NHMFL)
Tallahassee, Florida
Research Profile
Abstract:
Instead of focusing on a specific project, in this seminar I will provide a brief overview on recent research activities undertaken by my group at the NHMFL, including unpublished work. The goal is to provide enough basis for subsequent discussions with interested faculty members in the Department of Physics and Astronomy at the University of South Carolina. In the field of two-dimensional materials, I will discuss collaborative work involving i) the synthesis and subsequent optoelectronic characterization of high quality single-layer, as well as bi-layered, lateral heterostructures of transition metal dichalcogenides [1,2], ii) heterostructures resulting from the sulfurization of superconducting Mo2C that leads to interfaces between Mo2C and possible topological surface states in γ-MoC [3]. Concerning topological compounds, we focus on the synthesis of compounds predicted to possess topologically non-trivial electronic bands leading to, for example, Weyl and Dirac like quasiparticles, and on their characterization, for instance, through quantum oscillatory phenomena. We will briefly discuss new Dirac compounds [5] and the complex Dirac like dispersions of orthorhombic RhSi and cubic RhIn3Ge4 [6,7].
[1] P. Sahoo, S. Memaran, Y. Xin, L. Balicas, H. Gutierrez, Nature 553, 63 (2018).
[2] P. K. Sahoo, S. Memaran et al., ACS Nano 13, 12372 (2019).
|3] F. Zhang, W. Zheng et al., Proc. Natl. Acad. Sci. U.S.A. 117, 19685 (2020).
[5] K.-W. Chen et al., Phys. Rev. Lett. 120, 206401 (2018).
[6] S. Mozaffari et al., Phys. Rev. B 102, 115131 (2020).
[7] A. Flessa et al., Chem. Mater. (2021), in press; DOI:10.1021/acs.chemmater.0c03943
YouTube Recording
Department of Physics
College of Arts and Sciences
Florida State University
National High Magnetic Field Laboratory (NHMFL)
Tallahassee, Florida
Research Profile
Abstract:
Instead of focusing on a specific project, in this seminar I will provide a brief overview on recent research activities undertaken by my group at the NHMFL, including unpublished work. The goal is to provide enough basis for subsequent discussions with interested faculty members in the Department of Physics and Astronomy at the University of South Carolina. In the field of two-dimensional materials, I will discuss collaborative work involving i) the synthesis and subsequent optoelectronic characterization of high quality single-layer, as well as bi-layered, lateral heterostructures of transition metal dichalcogenides [1,2], ii) heterostructures resulting from the sulfurization of superconducting Mo2C that leads to interfaces between Mo2C and possible topological surface states in γ-MoC [3]. Concerning topological compounds, we focus on the synthesis of compounds predicted to possess topologically non-trivial electronic bands leading to, for example, Weyl and Dirac like quasiparticles, and on their characterization, for instance, through quantum oscillatory phenomena. We will briefly discuss new Dirac compounds [5] and the complex Dirac like dispersions of orthorhombic RhSi and cubic RhIn3Ge4 [6,7].
[1] P. Sahoo, S. Memaran, Y. Xin, L. Balicas, H. Gutierrez, Nature 553, 63 (2018).
[2] P. K. Sahoo, S. Memaran et al., ACS Nano 13, 12372 (2019).
|3] F. Zhang, W. Zheng et al., Proc. Natl. Acad. Sci. U.S.A. 117, 19685 (2020).
[5] K.-W. Chen et al., Phys. Rev. Lett. 120, 206401 (2018).
[6] S. Mozaffari et al., Phys. Rev. B 102, 115131 (2020).
[7] A. Flessa et al., Chem. Mater. (2021), in press; DOI:10.1021/acs.chemmater.0c03943
YouTube Recording
Dr. Larry Ford, Professor and Department Chair
Department of Physics and Astronomy
School of Arts and Sciences
Tufts University
Medford, Massachusetts
Research Profile
Abstract:
Although the vacuum state of a quantum field, such as the electromagnetic field, is an eigenstate of the total energy, the Hamiltonian, it is not an eigenstate of the local energy density. This leads to vacuum fluctuations of the energy density and similar operators. However, the energy density at a single space-time point is not meaningful, as any measurement records an average over finite regions of space and time. This average may be described as sampling functions which are nonzero in a finite interval, and the outcome of the measurement is very sensitive to the details of these functions. The associated probability distribution is a non-Gaussian function which decreases slowly, and leads to an enhanced probability for large quantum energy density fluctuations. These can in turn lead to large fluctuations of the gravitational field. Some possible effects of these fluctuations in the early universe, including primordial black hole formation, will be discussed. An analog model involving quantum density fluctuations in a fluid will also be described. Here the large density fluctuations might be detectable in light scattering experiments.
YouTube Recording
Department of Physics and Astronomy
School of Arts and Sciences
Tufts University
Medford, Massachusetts
Research Profile
Abstract:
Although the vacuum state of a quantum field, such as the electromagnetic field, is an eigenstate of the total energy, the Hamiltonian, it is not an eigenstate of the local energy density. This leads to vacuum fluctuations of the energy density and similar operators. However, the energy density at a single space-time point is not meaningful, as any measurement records an average over finite regions of space and time. This average may be described as sampling functions which are nonzero in a finite interval, and the outcome of the measurement is very sensitive to the details of these functions. The associated probability distribution is a non-Gaussian function which decreases slowly, and leads to an enhanced probability for large quantum energy density fluctuations. These can in turn lead to large fluctuations of the gravitational field. Some possible effects of these fluctuations in the early universe, including primordial black hole formation, will be discussed. An analog model involving quantum density fluctuations in a fluid will also be described. Here the large density fluctuations might be detectable in light scattering experiments.
YouTube Recording
Dr. Pawel Mazur, Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The physical nature of super-compact objects discovered in the merging binaries by LIGO/VIRGO gravitational wave detectors will be elaborated on. Some specific predictions have been already proposed for the future falsification by the LIGO-VIRGO-KAGRA gravitational wave detectors in the next few observational runs.I will present the No Hair result for the solution of Einstein equations describing the non-vacuum regular interior and the vacuum exterior of a spinning black hole. There are only two parameters characterizing the vacuum exterior and two parameters for the non-vacuum regular interior of a spinning black hole. These two sets of two parameters are connected by the matching condition for the interior and the exterior solutions on the apparent horizon. The solution depends on two parameters for which one can take the mass M and angular momentum J = Ma characterizing the vacuum exterior Kerr metric. The unique regular source of the Kerr gravitational field rotates rigidly with the angular velocity Ω equal to the angular velocity Ω H of the Kerr black hole horizon. The exterior vacuum solution is given by the well-known Kerr metric while the interior metric is completely new.My result settles the problem posed by R. P. Kerr in 1963 in the case of slow rotation. This is the No Hair result for the regular spinning black holes such as those indirectly observed in nature and thus it should have a bearing on the description of the final states of mergers of binary black holes detected by LIGO and Virgo (and soon KAGRA) gravitational wave detectors.
YouTube Recording
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The physical nature of super-compact objects discovered in the merging binaries by LIGO/VIRGO gravitational wave detectors will be elaborated on. Some specific predictions have been already proposed for the future falsification by the LIGO-VIRGO-KAGRA gravitational wave detectors in the next few observational runs.I will present the No Hair result for the solution of Einstein equations describing the non-vacuum regular interior and the vacuum exterior of a spinning black hole. There are only two parameters characterizing the vacuum exterior and two parameters for the non-vacuum regular interior of a spinning black hole. These two sets of two parameters are connected by the matching condition for the interior and the exterior solutions on the apparent horizon. The solution depends on two parameters for which one can take the mass M and angular momentum J = Ma characterizing the vacuum exterior Kerr metric. The unique regular source of the Kerr gravitational field rotates rigidly with the angular velocity Ω equal to the angular velocity Ω H of the Kerr black hole horizon. The exterior vacuum solution is given by the well-known Kerr metric while the interior metric is completely new.My result settles the problem posed by R. P. Kerr in 1963 in the case of slow rotation. This is the No Hair result for the regular spinning black holes such as those indirectly observed in nature and thus it should have a bearing on the description of the final states of mergers of binary black holes detected by LIGO and Virgo (and soon KAGRA) gravitational wave detectors.
YouTube Recording
Dr. Michael Osofsky, Section Head
United States Naval Research Laboratory
Washington, D.C.
Research Profile
Abstract:
Metamaterial approach to dielectric response engineering increases the critical temperature of a composite superconductor-dielectric system in the epsilon near zero (ENZ) and hyperbolic regimes. To create such metamaterial superconductors, three approaches were implemented. In the first approach, mixtures of tin and barium titanate nanoparticles of varying composition were used. An increase of the critical temperature of the order of 5% compared to bulk tin has been observed for a 40% volume fraction of barium titanate nanoparticles. In the second approach, we demonstrate the use of AI2O3-coated aluminum nanoparticles to form an ENZ core-shell metamaterial superconductor with a Tc that is three times that of pure aluminum. In the third approach, we demonstrate a similar Tc enhancement in thin AI/AI2O3 heterostructures that form a hyperbolic metamaterial superconductor.
These results open up numerous new possibilities of considerable Tc increase in other superconductors.
United States Naval Research Laboratory
Washington, D.C.
Research Profile
Abstract:
Metamaterial approach to dielectric response engineering increases the critical temperature of a composite superconductor-dielectric system in the epsilon near zero (ENZ) and hyperbolic regimes. To create such metamaterial superconductors, three approaches were implemented. In the first approach, mixtures of tin and barium titanate nanoparticles of varying composition were used. An increase of the critical temperature of the order of 5% compared to bulk tin has been observed for a 40% volume fraction of barium titanate nanoparticles. In the second approach, we demonstrate the use of AI2O3-coated aluminum nanoparticles to form an ENZ core-shell metamaterial superconductor with a Tc that is three times that of pure aluminum. In the third approach, we demonstrate a similar Tc enhancement in thin AI/AI2O3 heterostructures that form a hyperbolic metamaterial superconductor.
These results open up numerous new possibilities of considerable Tc increase in other superconductors.
Dr. Rocky Kolb, Arthur Holly Compton Distinguished Service Professor
Department of Astronomy and Astrophysics
Director of the Kavli Institute of Cosmological Physics
Co-Winner of the 2010 Dannie Heineman Prize for Astrophysics
University of Chicago
Chicago, Illinois
Research Profile
Abstract:
The big bang is a laboratory to explore the properties of particles that cannot be created in terrestrial laboratories. In addition to thermal processes, there is another source of cosmological particle production. In 1939, Erwin Schrödinger pointed out that particle-antiparticle pairs could be created merely by the violent expansion of space. The spontaneous appearance of particles from the vacuum so disturbed Schrödinger that he referred to it as an "alarming" phenomenon. The phenomenon is now thought to be the origin of density fluctuations produced in inflation as well as a background of gravitational waves. Gravitational particle production is a rich phenomenon, which continues to be explored.
YouTube Recording
Department of Astronomy and Astrophysics
Director of the Kavli Institute of Cosmological Physics
Co-Winner of the 2010 Dannie Heineman Prize for Astrophysics
University of Chicago
Chicago, Illinois
Research Profile
Abstract:
The big bang is a laboratory to explore the properties of particles that cannot be created in terrestrial laboratories. In addition to thermal processes, there is another source of cosmological particle production. In 1939, Erwin Schrödinger pointed out that particle-antiparticle pairs could be created merely by the violent expansion of space. The spontaneous appearance of particles from the vacuum so disturbed Schrödinger that he referred to it as an "alarming" phenomenon. The phenomenon is now thought to be the origin of density fluctuations produced in inflation as well as a background of gravitational waves. Gravitational particle production is a rich phenomenon, which continues to be explored.
YouTube Recording
Dr. Yuriy Pershin, Associate Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The study of resistive switching memory cells has been attracting a lot of attention due to their possible application as non-volatile memories, in neural networks, and even computing architectures. In 2008, it was suggested that all resistive-switching memory cells are memristors [Nature, 2008, 453, 80]. The latter are hypothetical, ideal devices whose resistance, as originally formulated, depends only on the net charge that traverses them. In my talk, I will introduce an unambiguous test we recently developed to determine whether a given physical system is indeed a memristor or not. The results of the test application to in-house fabricated Cu-SiO2 and commercially available electrochemical materialization cells indicate that the electrochemical metallization memory cells are not memristors [Adv. Electron. Mater. 2020, 2000010].
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The study of resistive switching memory cells has been attracting a lot of attention due to their possible application as non-volatile memories, in neural networks, and even computing architectures. In 2008, it was suggested that all resistive-switching memory cells are memristors [Nature, 2008, 453, 80]. The latter are hypothetical, ideal devices whose resistance, as originally formulated, depends only on the net charge that traverses them. In my talk, I will introduce an unambiguous test we recently developed to determine whether a given physical system is indeed a memristor or not. The results of the test application to in-house fabricated Cu-SiO2 and commercially available electrochemical materialization cells indicate that the electrochemical metallization memory cells are not memristors [Adv. Electron. Mater. 2020, 2000010].
Dr. Thomas Crawford, Professor
Dr. Scott Crittenden, Associate Professor
Dr. Yanwen Wu, Associate Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile - Dr. Crawford
Research Profile - Dr. Crittenden
Research Profile - Dr. Wu
Abstract:
During the past decade, the experimentalists of the SmartState Center for Experimental Nanoscale Physics have made significant contributions to understanding magnetic and multiferroic nanomaterials, exploring novel forms of surface magnetism, and studying quantum dot photonics. Examples include: Directed self-assembly of magnetic nanoparticles, surface magnetism in nominally non-magnetic materials, nanophotonics in quantum dot structures, and multiferroicity in Janus nanofibers. These activities have resulted in numerous publications, invited talks, book chapters, review articles, as well as a startup company that was sold to photonics giant Thorlabs in 2019.
In this colloquium, we will discuss selected results of these projects and collaborations and describe some future directions we would like to explore together. This presentation is in connection with the new SmartState Center chair hiring process.
Dr. Scott Crittenden, Associate Professor
Dr. Yanwen Wu, Associate Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile - Dr. Crawford
Research Profile - Dr. Crittenden
Research Profile - Dr. Wu
Abstract:
During the past decade, the experimentalists of the SmartState Center for Experimental Nanoscale Physics have made significant contributions to understanding magnetic and multiferroic nanomaterials, exploring novel forms of surface magnetism, and studying quantum dot photonics. Examples include: Directed self-assembly of magnetic nanoparticles, surface magnetism in nominally non-magnetic materials, nanophotonics in quantum dot structures, and multiferroicity in Janus nanofibers. These activities have resulted in numerous publications, invited talks, book chapters, review articles, as well as a startup company that was sold to photonics giant Thorlabs in 2019.
In this colloquium, we will discuss selected results of these projects and collaborations and describe some future directions we would like to explore together. This presentation is in connection with the new SmartState Center chair hiring process.
Dr. Yaroslaw Bazaliy, Associate Professor
Dr. Yuriy Pershin, Associate Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
During the past decade, the theorists of the SmartState Center for Experimental Nanoscale Physics have made significant contributions to the areas of spintronics, resistance switching memories, and 2D materials. Examples of this work include: the theory of spin noise spectroscopy, models and applications of emerging memory devices, prediction of kinks in buckled graphene, etc. These activities have resulted in numerous publications, research presentations, and invited talks.
In this colloquium, we will overview selected results of our work and discuss the future directions that can be explored. This presentation is in connection with the new SmartState Center chair hiring process.
Dr. Yuriy Pershin, Associate Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
During the past decade, the theorists of the SmartState Center for Experimental Nanoscale Physics have made significant contributions to the areas of spintronics, resistance switching memories, and 2D materials. Examples of this work include: the theory of spin noise spectroscopy, models and applications of emerging memory devices, prediction of kinks in buckled graphene, etc. These activities have resulted in numerous publications, research presentations, and invited talks.
In this colloquium, we will overview selected results of our work and discuss the future directions that can be explored. This presentation is in connection with the new SmartState Center chair hiring process.
Dr. Ward Plummer
Boyd Professor of Physics and Astronomy
Louisiana State University
Baton Rouge, Louisiana
Research Profile
Accolades:
Member of the National Academy of Sciences
Winner of Wayne B. Nottingham Prize, Davisson-Germer Prize in Surface Physics, and Medard W. Welch Award
Abstract:
The discovery of topological quantum materials has created a renaissance in surface physics. To understand the rebirth of surface physics requires a historical perspective. Surface physics in the United States has gone through wild oscillations in popularity. Surely the birth of modern surface physics was tied to vacuum technology, collimating in the 1932 Nobel Prize awarded to Irving Langmuir. Starting in the 1960s, surface chemistry and physics emerged as a key discipline in university departments, resulting in the 2007 Nobel Prize to Gerhard Ertl.
In this talk, I will trace the history of surface physics, illustrating the rebirth of surface physics in the 21st century with the discovery of enhanced surface superconductivity, the existence of topologically protected metallic helical electronic DIrac-like surface states, and the possible impact on quantum science and technology. Like the European Renaissance of the 14th and 15th centuries, the 21st century rebirth of surface physics is a combination of "new ideas" and "new technology."
Boyd Professor of Physics and Astronomy
Louisiana State University
Baton Rouge, Louisiana
Research Profile
Accolades:
Member of the National Academy of Sciences
Winner of Wayne B. Nottingham Prize, Davisson-Germer Prize in Surface Physics, and Medard W. Welch Award
Abstract:
The discovery of topological quantum materials has created a renaissance in surface physics. To understand the rebirth of surface physics requires a historical perspective. Surface physics in the United States has gone through wild oscillations in popularity. Surely the birth of modern surface physics was tied to vacuum technology, collimating in the 1932 Nobel Prize awarded to Irving Langmuir. Starting in the 1960s, surface chemistry and physics emerged as a key discipline in university departments, resulting in the 2007 Nobel Prize to Gerhard Ertl.
In this talk, I will trace the history of surface physics, illustrating the rebirth of surface physics in the 21st century with the discovery of enhanced surface superconductivity, the existence of topologically protected metallic helical electronic DIrac-like surface states, and the possible impact on quantum science and technology. Like the European Renaissance of the 14th and 15th centuries, the 21st century rebirth of surface physics is a combination of "new ideas" and "new technology."
Dr. Smita Mathur, Professor
Department of Astronomy
Ohio State University
Columbus, Ohio
Research Profile
Abstract:
The circumgalactic medium (CGM) is an important component of a galaxy, at the interface between the intergalactic medium and the galactic disk. Most of the mass of a galaxy is in this hot phase, which can be probed by X-ray emission and absorption. I will discuss the strides we made in understanding the physics of the CGM of the Milky Way using Chandra and XMM-Newton. Recently, using deep XMM-Newton observations, we discovered the hottest component of the CGM, about ten times hotter than ever before. We also found the gas to be enhanced in alpha-elements. In addition, we found non-solar abundance ratios. These results are informative about the chemical and thermal history of the CGM. One of the outstanding problems in understanding galaxy evolution is the relation between the properties of the galaxy and its CGM. I will discuss our preliminary results and compare them to theoretical simulations.
Department of Astronomy
Ohio State University
Columbus, Ohio
Research Profile
Abstract:
The circumgalactic medium (CGM) is an important component of a galaxy, at the interface between the intergalactic medium and the galactic disk. Most of the mass of a galaxy is in this hot phase, which can be probed by X-ray emission and absorption. I will discuss the strides we made in understanding the physics of the CGM of the Milky Way using Chandra and XMM-Newton. Recently, using deep XMM-Newton observations, we discovered the hottest component of the CGM, about ten times hotter than ever before. We also found the gas to be enhanced in alpha-elements. In addition, we found non-solar abundance ratios. These results are informative about the chemical and thermal history of the CGM. One of the outstanding problems in understanding galaxy evolution is the relation between the properties of the galaxy and its CGM. I will discuss our preliminary results and compare them to theoretical simulations.
Dr. Richard Creswick, Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
In this talk, I will focus on three fascinating puzzles involving the intersection of particle physics and cosmology:
1. Why is the neutron dipole moment at least ten orders of magnitude smaller than one might 'naturally' expect?
2. What is dark matter?
3. How do very extragalactic photons (TeV and above) from extragalactic BLAZARs manage to avoid pair-production in the intergalactic medium?
I will explain how the axion/ALP (axion-like particle) is a possible solution to each of these puzzles and discuss the experiments and astronomical observations that have placed bounds on the mass and coupling of the ALP to the electromagnetic field.
Finally, I will present a laboratory-based experiment, FPAS, designed to extend the search for ALPs into new parts of the ALP parameter space, and compare this to next-generation experiments being proposed.
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
In this talk, I will focus on three fascinating puzzles involving the intersection of particle physics and cosmology:
1. Why is the neutron dipole moment at least ten orders of magnitude smaller than one might 'naturally' expect?
2. What is dark matter?
3. How do very extragalactic photons (TeV and above) from extragalactic BLAZARs manage to avoid pair-production in the intergalactic medium?
I will explain how the axion/ALP (axion-like particle) is a possible solution to each of these puzzles and discuss the experiments and astronomical observations that have placed bounds on the mass and coupling of the ALP to the electromagnetic field.
Finally, I will present a laboratory-based experiment, FPAS, designed to extend the search for ALPs into new parts of the ALP parameter space, and compare this to next-generation experiments being proposed.
Dr. William E. Mustain, Professor
Department of Chemical Engineering
College of Engineering and Computing
University of South Carolina
Research Profile
Abstract:
Materials innovations have driven the development of multiple energy storage devices throughout our lifetime, but none of them have transformed our daily lives like the emergence of Li-ion batteries. Li-ion batteries find themselves integrated into nearly every part of our lives and have made high-power mobile computing and communication possible. Because of this, it makes sense that we would turn to Li-ion batteries for our next-generation storage needs - e.g. long-range electric vehicles, grid-scale storage of renewables, etc. Unfortunately, for some of these applications, particularly automotive, existing materials are insufficient to achieve the necessary energy density.
This talk will begin from a place that has brought renewed interest and celebration in the Li-ion battery community this year due to the 2019 Nobel Prize in Chemistry being awarded to Prof. Stanley Whittingham (Binghampton University), Prof. John Goodenough (University of Texas at Austin), and Dr. Akira Yoshino (Asahi Kasei Corporation) - with a brief discussion on the founding materials for Li-ion batteries. I will then talk about the limitations of existing materials to meet automotive demands as well as some of the safety issues that have come with attempts to meet energy density targets with packaging alone. The final part of this talk will discuss new materials and approaches to increase Li-ion battery energy density, with a particular focus on the anode material.
For more information about this project and the rest of our group, please visit http://www.mustainlab.com.
Department of Chemical Engineering
College of Engineering and Computing
University of South Carolina
Research Profile
Abstract:
Materials innovations have driven the development of multiple energy storage devices throughout our lifetime, but none of them have transformed our daily lives like the emergence of Li-ion batteries. Li-ion batteries find themselves integrated into nearly every part of our lives and have made high-power mobile computing and communication possible. Because of this, it makes sense that we would turn to Li-ion batteries for our next-generation storage needs - e.g. long-range electric vehicles, grid-scale storage of renewables, etc. Unfortunately, for some of these applications, particularly automotive, existing materials are insufficient to achieve the necessary energy density.
This talk will begin from a place that has brought renewed interest and celebration in the Li-ion battery community this year due to the 2019 Nobel Prize in Chemistry being awarded to Prof. Stanley Whittingham (Binghampton University), Prof. John Goodenough (University of Texas at Austin), and Dr. Akira Yoshino (Asahi Kasei Corporation) - with a brief discussion on the founding materials for Li-ion batteries. I will then talk about the limitations of existing materials to meet automotive demands as well as some of the safety issues that have come with attempts to meet energy density targets with packaging alone. The final part of this talk will discuss new materials and approaches to increase Li-ion battery energy density, with a particular focus on the anode material.
For more information about this project and the rest of our group, please visit http://www.mustainlab.com.
Dr. Dennis Bodewits, Associate Professor
Department of Physics
Auburn University
Auburn, Alabama
Research Profile
Abstract:
Comets are considered primitive left-overs from the era of planet formation. Most science questions therefore revolve around whether observed properties are primordial, i.e. representative of conditions during the era of planet formation, or whether they are caused by subsequent processing. Comets may also have delivered water and complex molecules to Earth and other planets in our solar system. FInally, the discovery that our solar system is frequently viewed by interstellar comets places comet science at the forefront of astrobiology.
This talk will take attendees on a tour of what we know about comets, what mysteries we need to solve, and how future spacecraft and telescopes could help us answer our questions.
Department of Physics
Auburn University
Auburn, Alabama
Research Profile
Abstract:
Comets are considered primitive left-overs from the era of planet formation. Most science questions therefore revolve around whether observed properties are primordial, i.e. representative of conditions during the era of planet formation, or whether they are caused by subsequent processing. Comets may also have delivered water and complex molecules to Earth and other planets in our solar system. FInally, the discovery that our solar system is frequently viewed by interstellar comets places comet science at the forefront of astrobiology.
This talk will take attendees on a tour of what we know about comets, what mysteries we need to solve, and how future spacecraft and telescopes could help us answer our questions.
Dr. Daniel Scolnic, Assistant Professor
Department of Physics
Duke University
Durham, North Carolina
Research Profile
Abstract:
In this talk, I will present the latest measurements of the expansion rate of the universe as well as its acceleration. I will focus on the use of Type Ia Supernovae, which continue to be an extremely powerful probe of the local universe. I will dive into the Hubble Constant Tension, now called a 'Crisis,' and give updates about all of the most recent results as well as what to expect within the next six months. I will also go over recent claims attempting to disprove confirmation of the accelerating universe. I will then discuss the next generation of telescopes and the supernova revolution we should be expecting in the next decade.
Department of Physics
Duke University
Durham, North Carolina
Research Profile
Abstract:
In this talk, I will present the latest measurements of the expansion rate of the universe as well as its acceleration. I will focus on the use of Type Ia Supernovae, which continue to be an extremely powerful probe of the local universe. I will dive into the Hubble Constant Tension, now called a 'Crisis,' and give updates about all of the most recent results as well as what to expect within the next six months. I will also go over recent claims attempting to disprove confirmation of the accelerating universe. I will then discuss the next generation of telescopes and the supernova revolution we should be expecting in the next decade.
Dr. Varsha Kulkarni, Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The 2019 Nobel Prize in Physics was awarded in part to Drs. Michel Mayor and Didier Queloz for their discovery of the first extrasolar planet around a normal star. Extrasolar planets (planets orbiting stars outside our solar system) are extremely challenging to find. Mayor and Queloz (then a graduate student) accomplished this extraordinary task using high-resolution optical spectroscopy. Their work showed that other planetary systems can differ starkly from our own solar system and opened the door to an avalanche of discoveries of other extrasolar planets. We now know of over 4,000 extrasolar planets, including hundreds of multi-planet systems.
I will describe the Nobel-winning discovery and how it was achieved. I will also summarize other techniques for detecting extrasolar planets and the huge progress made in recent years in not just inferring the existence of extrasolar planets, but also measuring their compositions. Finally, I will discuss some future directions and the question of why extrasolar planets is important for our civilization.
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The 2019 Nobel Prize in Physics was awarded in part to Drs. Michel Mayor and Didier Queloz for their discovery of the first extrasolar planet around a normal star. Extrasolar planets (planets orbiting stars outside our solar system) are extremely challenging to find. Mayor and Queloz (then a graduate student) accomplished this extraordinary task using high-resolution optical spectroscopy. Their work showed that other planetary systems can differ starkly from our own solar system and opened the door to an avalanche of discoveries of other extrasolar planets. We now know of over 4,000 extrasolar planets, including hundreds of multi-planet systems.
I will describe the Nobel-winning discovery and how it was achieved. I will also summarize other techniques for detecting extrasolar planets and the huge progress made in recent years in not just inferring the existence of extrasolar planets, but also measuring their compositions. Finally, I will discuss some future directions and the question of why extrasolar planets is important for our civilization.
Dr. J. Michael Shull, Professor
Department of Astrophysical and Planetary Sciences
University of Colorado (Boulder)
University of North Carolina (Chapel Hill)
Research Profile
Abstract:
I will review recent observations and theoretical estimates of the spatial extent of galaxies. Galaxies are defined as systems of stars and gas embedded in extended halos of dark mater and formed by the infall of smaller systems. Their sizes are determined by gravitational structures, gas dynamics, and chemical enrichment in heavy elements produced by stars and blown into extragalactic space by galactic winds. The full extent of galaxies remains poorly determined. The "virial radius" and "gravitational radius" provide estimates of the separation between collapsed structures in dynamical equilibrium and external infalling matter. Other measurements come from X-ray emission and ultraviolet absorption lines from metal-enriched gas in galactic halos. Astronomers have now identified large reservoirs of baryonic matter in the circumgalactic medium (CGM) and intergalactic medium (IGM) that contain 50-70% of the cosmological baryons formed in the Big Bang. The extent of the bound gas and dark matter around galaxies such as our Milky Way is approximately 200 kpc (650,000 light years). Investigators of physical processes at the "edge of galaxies" are crucial for interpreting new observations of the CGM and IGM, and their role in sustaining the star formation in galaxies.
Department of Astrophysical and Planetary Sciences
University of Colorado (Boulder)
University of North Carolina (Chapel Hill)
Research Profile
Abstract:
I will review recent observations and theoretical estimates of the spatial extent of galaxies. Galaxies are defined as systems of stars and gas embedded in extended halos of dark mater and formed by the infall of smaller systems. Their sizes are determined by gravitational structures, gas dynamics, and chemical enrichment in heavy elements produced by stars and blown into extragalactic space by galactic winds. The full extent of galaxies remains poorly determined. The "virial radius" and "gravitational radius" provide estimates of the separation between collapsed structures in dynamical equilibrium and external infalling matter. Other measurements come from X-ray emission and ultraviolet absorption lines from metal-enriched gas in galactic halos. Astronomers have now identified large reservoirs of baryonic matter in the circumgalactic medium (CGM) and intergalactic medium (IGM) that contain 50-70% of the cosmological baryons formed in the Big Bang. The extent of the bound gas and dark matter around galaxies such as our Milky Way is approximately 200 kpc (650,000 light years). Investigators of physical processes at the "edge of galaxies" are crucial for interpreting new observations of the CGM and IGM, and their role in sustaining the star formation in galaxies.
Dr. Craig Group, Associate Professor
Experimental High Energy Physics Group
Department of Physics
University of Virginia
Charlottesville, Virginia
Research Profile
Abstract:
In a sense, the muon has become a thorn in the side of particle physicists since its discovery in 1936. Still, we seek answers related to questions of flavor. Why three families? Why are the lepton masses so different? Who ordered that?
Experiments searching for charged lepton flavor violation seemed to run out of sensitivity gains in the 1990s. However, a re-birth is ongoing! A new series of experiments, led by new technologies, are poised to push sensitivities down several orders of magnitude. Soon, the muon sector may lead to discoveries that will help answer the most fundamental questions of particle physics.
Experimental High Energy Physics Group
Department of Physics
University of Virginia
Charlottesville, Virginia
Research Profile
Abstract:
In a sense, the muon has become a thorn in the side of particle physicists since its discovery in 1936. Still, we seek answers related to questions of flavor. Why three families? Why are the lepton masses so different? Who ordered that?
Experiments searching for charged lepton flavor violation seemed to run out of sensitivity gains in the 1990s. However, a re-birth is ongoing! A new series of experiments, led by new technologies, are poised to push sensitivities down several orders of magnitude. Soon, the muon sector may lead to discoveries that will help answer the most fundamental questions of particle physics.
Dr. Peter Mättig, Professor
Experimental Particle Physics Division
Department of Physics
University of Bonn
Bonn, Germany
Research Profile
Abstract:
The Large Hadron Collider (LHC) at the European Center for Particle Physics (CERN - Geneva, Switzerland) probes matter at the highest accelerator energy ever reached. In the past ten years of its operation, it has pushed the boundaries of the Standard Model of particle physics to stunning precision, and, by the discovery of the Higgs boson, has found its last building block. But, despite hopes and expectations, it has, at yet, not found any glimpse of how to move beyond the Standard Model. The current situation of particle physics at the crossroad raises several questions of philosophical interest that are addressed in a large interdisciplinary research group in Germany.
In this talk, I will provide an overview over experimentation at the LHC, the current status of particle physics, and the challenges that it faces. I will then highlight a few questions addressed in our philosophy project, especially the role of models and the trend towards model independent experimentation.
Experimental Particle Physics Division
Department of Physics
University of Bonn
Bonn, Germany
Research Profile
Abstract:
The Large Hadron Collider (LHC) at the European Center for Particle Physics (CERN - Geneva, Switzerland) probes matter at the highest accelerator energy ever reached. In the past ten years of its operation, it has pushed the boundaries of the Standard Model of particle physics to stunning precision, and, by the discovery of the Higgs boson, has found its last building block. But, despite hopes and expectations, it has, at yet, not found any glimpse of how to move beyond the Standard Model. The current situation of particle physics at the crossroad raises several questions of philosophical interest that are addressed in a large interdisciplinary research group in Germany.
In this talk, I will provide an overview over experimentation at the LHC, the current status of particle physics, and the challenges that it faces. I will then highlight a few questions addressed in our philosophy project, especially the role of models and the trend towards model independent experimentation.
Dr. Revaz Ramazashvili
Laboratoire de Physique Théorique
Université Paul Sabatier
Toulouse, France
Research Profile
Abstract:
We find that the Néel state of the layered organic conductor k-(BETS)2FeBr4 shows no spin modulation of the Shubnikov-de Haas oscillations, contrary to the paramagnetic state of the same material. This is evidence of spin degeneracy of Landau levels – a direct manifestation of the generic Zeeman spin-orbit
coupling, predicted for antiferromagnetic conductors. Likewise, we find no spin modulation in the angle dependence of the slow Shubnikov-de Haas oscillations in the optimally electron-doped cuprate Nd2-xCexCuO4. This points to the presence of Néel order in this superconductor even at optimal doping.
Laboratoire de Physique Théorique
Université Paul Sabatier
Toulouse, France
Research Profile
Abstract:
We find that the Néel state of the layered organic conductor k-(BETS)2FeBr4 shows no spin modulation of the Shubnikov-de Haas oscillations, contrary to the paramagnetic state of the same material. This is evidence of spin degeneracy of Landau levels – a direct manifestation of the generic Zeeman spin-orbit
coupling, predicted for antiferromagnetic conductors. Likewise, we find no spin modulation in the angle dependence of the slow Shubnikov-de Haas oscillations in the optimally electron-doped cuprate Nd2-xCexCuO4. This points to the presence of Néel order in this superconductor even at optimal doping.
Dr. Laurie E. McNeil
Bernard Gray Distinguished Professor
Department of Physics and Astronomy
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina
Research Profile
Abstract:
Members of the professoriate have a professional obligation to carry out our educational mission as effectively as possible (given the constraints of our circumstances), to maximize the benefit that students receive from our instruction. As physicists, this obliges us to make use of research findings from cognitive science and physics education research.
In this presentation, I will describe how I used these findings to transform my own work in the classroom and to lead comprehensive change in teaching and learning in my department. I will conclude with reflections on the elements that were crucial to the success of this institutional-scale transformation.
Bernard Gray Distinguished Professor
Department of Physics and Astronomy
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina
Research Profile
Abstract:
Members of the professoriate have a professional obligation to carry out our educational mission as effectively as possible (given the constraints of our circumstances), to maximize the benefit that students receive from our instruction. As physicists, this obliges us to make use of research findings from cognitive science and physics education research.
In this presentation, I will describe how I used these findings to transform my own work in the classroom and to lead comprehensive change in teaching and learning in my department. I will conclude with reflections on the elements that were crucial to the success of this institutional-scale transformation.
Dr. Megan Donahue, Professor
Department of Physics and Astronomy
Michigan State University
President of the American Astronomical Society
Research Profile
Abstract:
Most, if not all, of the galaxies in the universe host a supermassive black hole in the center. The masses of these black holes are correlated with the masses of the galaxies, or at least with the masses of the "bulge" components of the galaxies. Simulations of galaxy formation track how dark matter and baryons interact gravitationally, assembling the network of galaxies, clusters of galaxies, voids, and filaments that we observe today. Using our current understanding of the mean density of baryonic matter and dark matter, and of the effects of the accelerated expansion/dark energy, we now have a pretty good idea about how the largest structures emerged from the nearly uniform sea of tiny fluctuations that we can see in the cosmic microwave background. However, we demand more from these models. We would like to be able to explain what we observe, and that means explaining why, for example, the baryons don't make more stars than they do, why galaxies of about the mass of that of the Milky Way are the best at forming stars (yet still under perform based on expectations), and why the mass of a central black hole is affected by the mass of its host galaxy. The answers are all related. I will discuss a framework for thinking and talking about these issues, a framework useful for framing useful questions to apply to the simulations and next observations, and plans for the next space observatory.
Department of Physics and Astronomy
Michigan State University
President of the American Astronomical Society
Research Profile
Abstract:
Most, if not all, of the galaxies in the universe host a supermassive black hole in the center. The masses of these black holes are correlated with the masses of the galaxies, or at least with the masses of the "bulge" components of the galaxies. Simulations of galaxy formation track how dark matter and baryons interact gravitationally, assembling the network of galaxies, clusters of galaxies, voids, and filaments that we observe today. Using our current understanding of the mean density of baryonic matter and dark matter, and of the effects of the accelerated expansion/dark energy, we now have a pretty good idea about how the largest structures emerged from the nearly uniform sea of tiny fluctuations that we can see in the cosmic microwave background. However, we demand more from these models. We would like to be able to explain what we observe, and that means explaining why, for example, the baryons don't make more stars than they do, why galaxies of about the mass of that of the Milky Way are the best at forming stars (yet still under perform based on expectations), and why the mass of a central black hole is affected by the mass of its host galaxy. The answers are all related. I will discuss a framework for thinking and talking about these issues, a framework useful for framing useful questions to apply to the simulations and next observations, and plans for the next space observatory.
Dr. Monique Aller, Assistant Professor
Department of Physics and Astronomy
Georgia Southern University
Statesboro, Georgia
Research Profile
Abstract:
Interstellar dust grains comprise a relatively small percentage of the total galaxy mass, but they significantly impact both the appearance of the galaxy as well as many of the physical processes important for the formation of stars and evolution of the galaxy. The physical properties of these dust grains, including their composition, size, shape, and spatial distribution may vary both within a galaxy and from galaxy-to-galaxy. Absorption lines in the spectra of distant quasars whose sightlines pass through foreground galaxies provide a valuable tool to simultaneously probe the dust and gas compositions of the interstellar medium in both local and more distant galaxies.
I will discuss two ongoing collaborative research programs exploiting archival multi-wavelength data to explore the silicate and carbonaceous dust grain properties in galaxies probed by quasar absorption systems. I will present results from our work using Spitzer Space Telescope infrared spectra to study interstellar silicate dust grain properties in both local and distant quasar absorption systems and discuss our findings that silicate dust grain properties in distant galaxies can differ relative to one another and relative to those in the Milky Way.
Department of Physics and Astronomy
Georgia Southern University
Statesboro, Georgia
Research Profile
Abstract:
Interstellar dust grains comprise a relatively small percentage of the total galaxy mass, but they significantly impact both the appearance of the galaxy as well as many of the physical processes important for the formation of stars and evolution of the galaxy. The physical properties of these dust grains, including their composition, size, shape, and spatial distribution may vary both within a galaxy and from galaxy-to-galaxy. Absorption lines in the spectra of distant quasars whose sightlines pass through foreground galaxies provide a valuable tool to simultaneously probe the dust and gas compositions of the interstellar medium in both local and more distant galaxies.
I will discuss two ongoing collaborative research programs exploiting archival multi-wavelength data to explore the silicate and carbonaceous dust grain properties in galaxies probed by quasar absorption systems. I will present results from our work using Spitzer Space Telescope infrared spectra to study interstellar silicate dust grain properties in both local and distant quasar absorption systems and discuss our findings that silicate dust grain properties in distant galaxies can differ relative to one another and relative to those in the Milky Way.
Dr. Massimiliano Di Ventra, Professor
Department of Physics
University of California, San Diego
La Jolla, California
Research Profile
Abstract:
It is well known that physical phenomena may be of great help in computing some difficult problems efficiently. A typical example is prime factorization that may be solved in polynomial time by exploiting quantum entanglement on a quantum computer. There are, however, other types of (non-quantum) physical properties that one may leverage to compute efficiently a wide range of hard problems. In this talk, I will discuss how to employ one such property, memory (time non-locality), in a novel physics-based approach to computation: Memcomputing. As examples, I will show the efficient solution of prime factorization, the search version of the subset-sum problem, approximations to the Max-SAT, and the ground state of Ising spin glasses, using self-organizing logic gates, namely gates that self-organize to satisfy their logical proposition. I will also show that these machines take advantage of the long-range order that develops during their transient dynamics in order to tackle the above problems and are robust against noise and disorder. The digital memcomputing machines we propose can be efficiently simulated, are scalable, and can be easily realized with available nanotechnology components. Work supported in part by MemComputing, Inc. (www.memcpu.com) and CMRR.
Dr. Di Ventra's visit to USC is supported by the Office of the Provost's Visiting Scholars Grant Program.
Department of Physics
University of California, San Diego
La Jolla, California
Research Profile
Abstract:
It is well known that physical phenomena may be of great help in computing some difficult problems efficiently. A typical example is prime factorization that may be solved in polynomial time by exploiting quantum entanglement on a quantum computer. There are, however, other types of (non-quantum) physical properties that one may leverage to compute efficiently a wide range of hard problems. In this talk, I will discuss how to employ one such property, memory (time non-locality), in a novel physics-based approach to computation: Memcomputing. As examples, I will show the efficient solution of prime factorization, the search version of the subset-sum problem, approximations to the Max-SAT, and the ground state of Ising spin glasses, using self-organizing logic gates, namely gates that self-organize to satisfy their logical proposition. I will also show that these machines take advantage of the long-range order that develops during their transient dynamics in order to tackle the above problems and are robust against noise and disorder. The digital memcomputing machines we propose can be efficiently simulated, are scalable, and can be easily realized with available nanotechnology components. Work supported in part by MemComputing, Inc. (www.memcpu.com) and CMRR.
Dr. Di Ventra's visit to USC is supported by the Office of the Provost's Visiting Scholars Grant Program.
Dr. Leonid Pryadko, Professor
Department of Physics and Astronomy
University of California, Riverside
Riverside, California
Research Profile
Abstract:
I will give an elementary overview of the current state of the art in quantum error correction, one of the key enabling technologies for scalable quantum computation. How is it possible to protect a superposition state with continuously varying complex coefficients? How will fault-tolerant quantum error correction work in practice? What is it that commercial companies are trying to achieve in this field? And what are the major open questions in theory, experiment, and architecture of quantum computers?
Department of Physics and Astronomy
University of California, Riverside
Riverside, California
Research Profile
Abstract:
I will give an elementary overview of the current state of the art in quantum error correction, one of the key enabling technologies for scalable quantum computation. How is it possible to protect a superposition state with continuously varying complex coefficients? How will fault-tolerant quantum error correction work in practice? What is it that commercial companies are trying to achieve in this field? And what are the major open questions in theory, experiment, and architecture of quantum computers?
Dr. Oleg Tchernyshyov, Professor
Department of Physics and Astronomy
Johns Hopkins University
Baltimore, Maryland
Research Profile
Abstract:
Magnets host a variety of solitons that are stable for topological reasons: domain walls, vortices, and skyrmions, to name a few. Because of their stability, topological solitons can potentially be used for storing and processing information. This motivates us to build economic, yet realistic models of soliton dynamics in magnets (e.g. a domain wall in a ferromagnetic wire can be pictured as a bead on a string, which can move along the string and rotate about its axis). Its mechanics is counterintuitive: it rotates when pushed and moves when twisted. I will review basic models of magnetic solitons in one and two dimensions, including classic examples as well as new results.
Department of Physics and Astronomy
Johns Hopkins University
Baltimore, Maryland
Research Profile
Abstract:
Magnets host a variety of solitons that are stable for topological reasons: domain walls, vortices, and skyrmions, to name a few. Because of their stability, topological solitons can potentially be used for storing and processing information. This motivates us to build economic, yet realistic models of soliton dynamics in magnets (e.g. a domain wall in a ferromagnetic wire can be pictured as a bead on a string, which can move along the string and rotate about its axis). Its mechanics is counterintuitive: it rotates when pushed and moves when twisted. I will review basic models of magnetic solitons in one and two dimensions, including classic examples as well as new results.
Dr. Ashot Gasparian, Professor
Department of Physics
North Carolina A&T State University
Greensboro, North Carolina
Research Profile
Abstract:
Two new extremely high precision measurements of the proton rms charge radius performed in 2010-2012 with muonic hydrogen atom demonstrated up to six standard deviations smaller values than the accepted average from all previous experiments performed with different methods on regular hydrogen. This discrepancy triggered the well known "proton radius puzzle" in hadronic physics for the last several years. To address this puzzle, the PRad collaboration in May-June 2016 performed a novel magnetic-spectrometer-free ep-scattering experiment in Hall B at Jefferson Laboratory accumulating high statistics and a rich experimental data set. The specifics of the PRad experiment and the preliminary physics results, including the extracted proton radius, will be presented and discussed in this talk.
Department of Physics
North Carolina A&T State University
Greensboro, North Carolina
Research Profile
Abstract:
Two new extremely high precision measurements of the proton rms charge radius performed in 2010-2012 with muonic hydrogen atom demonstrated up to six standard deviations smaller values than the accepted average from all previous experiments performed with different methods on regular hydrogen. This discrepancy triggered the well known "proton radius puzzle" in hadronic physics for the last several years. To address this puzzle, the PRad collaboration in May-June 2016 performed a novel magnetic-spectrometer-free ep-scattering experiment in Hall B at Jefferson Laboratory accumulating high statistics and a rich experimental data set. The specifics of the PRad experiment and the preliminary physics results, including the extracted proton radius, will be presented and discussed in this talk.
Dr. Raul Briceno, Assistant Professor
Department of Physics
Old Dominion University
Joint Theory Staff Member at Jefferson Laboratory
Norfolk, Virginia
Research Profile
Abstract:
At the core of everyday matter is a complex inner world of subatomic particles. In particular, the nuclei of atoms are made of protons and neutrons, which are themselves made of even smaller particles known as quarks and gluons. Thanks to experiments, like the ones being carried out at Jefferson Lab, we have been able to peer inside and deduce the guiding principles for the behavior of quarks and gluons. This knowledge has been formalized into a fundamental theory of the strong nuclear force, Quantum Chromodynamics (QCD). However, despite having the theory in place for over 40 years, the connection between QCD and experiment has been historically limited by the fact that the strong nuclear force is "strongly interacting." In this talk, I will discuss recent theoretical progress that is finally allowing us to directly extract the same observables from QCD that are measured in experiment.
Department of Physics
Old Dominion University
Joint Theory Staff Member at Jefferson Laboratory
Norfolk, Virginia
Research Profile
Abstract:
At the core of everyday matter is a complex inner world of subatomic particles. In particular, the nuclei of atoms are made of protons and neutrons, which are themselves made of even smaller particles known as quarks and gluons. Thanks to experiments, like the ones being carried out at Jefferson Lab, we have been able to peer inside and deduce the guiding principles for the behavior of quarks and gluons. This knowledge has been formalized into a fundamental theory of the strong nuclear force, Quantum Chromodynamics (QCD). However, despite having the theory in place for over 40 years, the connection between QCD and experiment has been historically limited by the fact that the strong nuclear force is "strongly interacting." In this talk, I will discuss recent theoretical progress that is finally allowing us to directly extract the same observables from QCD that are measured in experiment.
Dr. Alexander Monin
Maître Assistant at the University of Geneva
Geneva, Switzerland
Research Profile
Abstract:
Despite undoubted success of the Standard Model of particle physics, we are absolutely certain that it cannot be the ultimate theory of nature. Several experimental puzzles indicate that there should be new particles. Two scenarios for why new physics does not currently manifest itself at accelerators are either new particles are too heavy or they are light, but very weakly interacting with the Standard Model particles. The two scenarios lead to deep theoretical questions.
In this talk, I will present what these questions are and will discuss how non-perturbative methods in quantum field theory may help to address them.
Maître Assistant at the University of Geneva
Geneva, Switzerland
Research Profile
Abstract:
Despite undoubted success of the Standard Model of particle physics, we are absolutely certain that it cannot be the ultimate theory of nature. Several experimental puzzles indicate that there should be new particles. Two scenarios for why new physics does not currently manifest itself at accelerators are either new particles are too heavy or they are light, but very weakly interacting with the Standard Model particles. The two scenarios lead to deep theoretical questions.
In this talk, I will present what these questions are and will discuss how non-perturbative methods in quantum field theory may help to address them.
Dr. Karen Livesey, Associate Professor
Department of Physics and Energy Science
University of Colorado at Colorado Springs
Colorado Springs, Colorado
Research Profile
Abstract:
Magnetic nanoparticles are used as drug-delivery systems, to kill cancer tumors by heating, and even to self-assemble optical diffraction gratings. There are many open questions about how the magnetization of these nanoparticles relaxes, both for individual particles and when they strongly interact with one another.
In the first half of this talk, I will discuss a new analytic method [1] to fit the magnetization versus temperature measurements of non-interacting particles, which leads to a dramatic reinterpretation of some literature results. In the second half of the talk, I will describe Langevin simulations of strongly interacting magnetic nanoparticles in fluids and show some of the exotic and varied dynamics that can result. This is important because a small change in the fluid environment can lead to large differences in the nanoparticle efficacy for the biomedical and technological applications that are listed above.
[1] Livesey, KL, Ruta S, Anderson NR, Baldomir D, Chantrell RW, and Serantes D. "Beyond the blocking model to fit nanoparticle ZFC/FC magnetisation curves." Scientific reports 8, 11166 (2018).
Bio: Karen Livesey is the first female Associate Professor of Physics in the University of Colorado at Colorado Springs' 53-year history. She is an award-winning teacher and theoretical physicist who specializes in studying nano-magnets. Karen received her Ph.D. in 2009 from the University of Western Australia. Her research is supported by the U.S. National Science Foundation and the U.K. Royal Society. She is a 2018-2019 Emmy Noether Fellow at the Perimeter Institute for Theoretical Physics in Canada.
Department of Physics and Energy Science
University of Colorado at Colorado Springs
Colorado Springs, Colorado
Research Profile
Abstract:
Magnetic nanoparticles are used as drug-delivery systems, to kill cancer tumors by heating, and even to self-assemble optical diffraction gratings. There are many open questions about how the magnetization of these nanoparticles relaxes, both for individual particles and when they strongly interact with one another.
In the first half of this talk, I will discuss a new analytic method [1] to fit the magnetization versus temperature measurements of non-interacting particles, which leads to a dramatic reinterpretation of some literature results. In the second half of the talk, I will describe Langevin simulations of strongly interacting magnetic nanoparticles in fluids and show some of the exotic and varied dynamics that can result. This is important because a small change in the fluid environment can lead to large differences in the nanoparticle efficacy for the biomedical and technological applications that are listed above.
[1] Livesey, KL, Ruta S, Anderson NR, Baldomir D, Chantrell RW, and Serantes D. "Beyond the blocking model to fit nanoparticle ZFC/FC magnetisation curves." Scientific reports 8, 11166 (2018).
Bio: Karen Livesey is the first female Associate Professor of Physics in the University of Colorado at Colorado Springs' 53-year history. She is an award-winning teacher and theoretical physicist who specializes in studying nano-magnets. Karen received her Ph.D. in 2009 from the University of Western Australia. Her research is supported by the U.S. National Science Foundation and the U.K. Royal Society. She is a 2018-2019 Emmy Noether Fellow at the Perimeter Institute for Theoretical Physics in Canada.
Dr. Andrey Katz
Long-Duration Staff at CERN
Professor Titulaire at the University of Geneva
Geneva, Switzerland
Research Profile
All currently observed phenomena are consistently explained by the Standard Model (SM) of particle physics. However, there are good reasons, both experimental and theoretical, to consider Physics Beyond the SM at the TeV scale. The SM violates the principle of naturalness, which is a fundamental theoretical problem. I will explain this problem and discuss experimental strategies for testing some of its possible solutions.
Abstract:
One is a popular scenario, supersymmetry, which involves a major extension of space-time symmetry and manifests itself in new particles with SM charges at collider. Another solution that I will discuss is the Twin Higgs, which in general predicts sterile particles at colliders. Remarkably, I will demonstrate that it also gives rise to observable signals. Both supersymmetry and the twin Higgs scenario have their own challenges and I will present novel strategies for both of these scenarios. The SM alone cannot account for observed matter-antimatter symmetry and requires new physics. I will analyze the possibility of generating the baryon asymmetry during the Electroweak phase transition and show that this idea can be probed at the LHC and future colliders via higgs precision measurement. I will also present a novel mechanism for generating the baryon asymmetry at temperatures below the electroweak temperature, which can be probed via the gravitational wave signals in future interferometers.
Finally, the SM does not have a dark matter candidate, but it can naturally be accommodated by certain extensions of the SM at the TeV scale. I will review some of these scenarios and emphasize the experimental signatures with an emphasis on the gravitational lensing.
Long-Duration Staff at CERN
Professor Titulaire at the University of Geneva
Geneva, Switzerland
Research Profile
All currently observed phenomena are consistently explained by the Standard Model (SM) of particle physics. However, there are good reasons, both experimental and theoretical, to consider Physics Beyond the SM at the TeV scale. The SM violates the principle of naturalness, which is a fundamental theoretical problem. I will explain this problem and discuss experimental strategies for testing some of its possible solutions.
Abstract:
One is a popular scenario, supersymmetry, which involves a major extension of space-time symmetry and manifests itself in new particles with SM charges at collider. Another solution that I will discuss is the Twin Higgs, which in general predicts sterile particles at colliders. Remarkably, I will demonstrate that it also gives rise to observable signals. Both supersymmetry and the twin Higgs scenario have their own challenges and I will present novel strategies for both of these scenarios. The SM alone cannot account for observed matter-antimatter symmetry and requires new physics. I will analyze the possibility of generating the baryon asymmetry during the Electroweak phase transition and show that this idea can be probed at the LHC and future colliders via higgs precision measurement. I will also present a novel mechanism for generating the baryon asymmetry at temperatures below the electroweak temperature, which can be probed via the gravitational wave signals in future interferometers.
Finally, the SM does not have a dark matter candidate, but it can naturally be accommodated by certain extensions of the SM at the TeV scale. I will review some of these scenarios and emphasize the experimental signatures with an emphasis on the gravitational lensing.
Dr. Kimberly Boddy, Postdoctoral Fellow
Henry A. Rowland Department of Physics and Astronomy
Johns Hopkins University
Baltimore, Maryland
Research Profile
Abstract:
There is overwhelming evidence for the existence of dark matter. It plays a crucial role in the formation of structure in the Universe, yet little is known about its properties beyond gravitational effects. In this talk, I will discuss the current and future prospects of understanding the fundamental nature of dark matter using observations in cosmology and astrophysics. These observations offer glimpses into different cosmic eras that may shed light on the mystery of dark matter.
Henry A. Rowland Department of Physics and Astronomy
Johns Hopkins University
Baltimore, Maryland
Research Profile
Abstract:
There is overwhelming evidence for the existence of dark matter. It plays a crucial role in the formation of structure in the Universe, yet little is known about its properties beyond gravitational effects. In this talk, I will discuss the current and future prospects of understanding the fundamental nature of dark matter using observations in cosmology and astrophysics. These observations offer glimpses into different cosmic eras that may shed light on the mystery of dark matter.
Dr. Igor Altfeder
Department of Physics
The Ohio State University
Columbus, Ohio
Research Profile
Abstract:
Many-body interactions in quantum materials are important not only for condensed matter physics; they are also relevant to the phenomena in high energy physics, cosmology, and biological physics. Our approach for studies of nanoscale interactions is based on scanning tunneling microscopy (STM). This presentation will describe the STM experiments with quasi-freestanding layers of two-dimensional semiconductor WSe2. They revealed the existence of room-temperature optical phonon condensate mediated by phonon scattering and interactions at resonant defects. The real space Bose-Einstein condensation manifests itself in synchronization of phonon phases and formation of collective condensate phase with unusually large, macroscopic coherence time. This coherent state of matter plays an important role in biological physics where it is known as Frohlich condensation.
Department of Physics
The Ohio State University
Columbus, Ohio
Research Profile
Abstract:
Many-body interactions in quantum materials are important not only for condensed matter physics; they are also relevant to the phenomena in high energy physics, cosmology, and biological physics. Our approach for studies of nanoscale interactions is based on scanning tunneling microscopy (STM). This presentation will describe the STM experiments with quasi-freestanding layers of two-dimensional semiconductor WSe2. They revealed the existence of room-temperature optical phonon condensate mediated by phonon scattering and interactions at resonant defects. The real space Bose-Einstein condensation manifests itself in synchronization of phonon phases and formation of collective condensate phase with unusually large, macroscopic coherence time. This coherent state of matter plays an important role in biological physics where it is known as Frohlich condensation.
Remarks by Dr. Ralf Gothe, Dr. Frank Avignone, Dr. Richard Creswick, etc.
Abstract:
This colloquium will be devoted to the memory of Professor Horacio Farach, a long time and distinguished member of our faculty, who passed away on December 29, 2018. Professor Farach came to USC in 1967 as a Visiting Professor following a brutal military coup in his home country of Argentina. On July 29, 1966, the "night of the long sticks," hundreds of students and faculty of the University of Buenos Aires were attacked by police wielding batons and arrested. About 1,400 faculty resigned in protest and 300 went into exile. Many of these exiled professors found positions in the U.S. and so Horacio came to South Carolina.
Professor Farach was tenured at Associate Professor in 1968 and had a distinguished career at USC, winning the Russell Research Award, the Jesse W. Beams Medal of the APS, and several high-level international honors, including the presidential level Luis Leloir Medal of Argentina (1966) and the "Mayores Notables Argentinos" awarded by the National Assembly of Argentina (similar to the U.S. Medal of Freedom) in 2013. In addition, he won three teaching awards at USC. He served as Graduate Director for 18 years and as both Assistant and later Associate Department Chair of our department under Frank Avignone. There were many interesting turns of events in his life that will make this lecture interesting. He was a dynamite personality packed tightly into 150 pounds. He will be missed by his friends, family, and many students.
Abstract:
This colloquium will be devoted to the memory of Professor Horacio Farach, a long time and distinguished member of our faculty, who passed away on December 29, 2018. Professor Farach came to USC in 1967 as a Visiting Professor following a brutal military coup in his home country of Argentina. On July 29, 1966, the "night of the long sticks," hundreds of students and faculty of the University of Buenos Aires were attacked by police wielding batons and arrested. About 1,400 faculty resigned in protest and 300 went into exile. Many of these exiled professors found positions in the U.S. and so Horacio came to South Carolina.
Professor Farach was tenured at Associate Professor in 1968 and had a distinguished career at USC, winning the Russell Research Award, the Jesse W. Beams Medal of the APS, and several high-level international honors, including the presidential level Luis Leloir Medal of Argentina (1966) and the "Mayores Notables Argentinos" awarded by the National Assembly of Argentina (similar to the U.S. Medal of Freedom) in 2013. In addition, he won three teaching awards at USC. He served as Graduate Director for 18 years and as both Assistant and later Associate Department Chair of our department under Frank Avignone. There were many interesting turns of events in his life that will make this lecture interesting. He was a dynamite personality packed tightly into 150 pounds. He will be missed by his friends, family, and many students.
Dr. Yanwen Wu, Assistant Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The 2018 Nobel Prize in Physics celebrates the invention of two important tools in optics: the optical tweezers and the chirped-pulse amplification (CPA) technique. The prize is shared by three physicists: Donna Strickland (CPA), Gerard Mourou (CPA), and Arthur Ashkin (optical tweezers). I will give a brief history of the development of tools made of light and provide an overview of the physics behind these latest additions to the light toolbox and their amazingly broad applications in areas ranging from basic research to everyday life.
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The 2018 Nobel Prize in Physics celebrates the invention of two important tools in optics: the optical tweezers and the chirped-pulse amplification (CPA) technique. The prize is shared by three physicists: Donna Strickland (CPA), Gerard Mourou (CPA), and Arthur Ashkin (optical tweezers). I will give a brief history of the development of tools made of light and provide an overview of the physics behind these latest additions to the light toolbox and their amazingly broad applications in areas ranging from basic research to everyday life.
Prof. Valery Nesvizhevsky, Staff Scientist
Science Division
Institute Laue-Langevin (ILL)
Grenoble, France
Research Profile
Abstract:
Gravitational quantum states (GQS) are traps for ultracold massive particles with gravity on top and a specularly reflecting mirror with a sharply changing surface potential on bottom. Ultralow energies make this system very sensitive to any tiny interactions and large sizes simplify the experimental techniques. GQS was discovered in experiments with ultracold neutrons (UCN) in 2002 and since then, they are actively used by several research groups (qBounce, Tokyo, GRANIT) at ILL, Grenoble.
While repulsive neutron-nuclei optical potential of many materials totally reflect UCN from surfaces, attractive van der Waals/Casimir-Polder potentials can also reflect ultracold atoms and molecules at surface due to quantum reflection. In contrast to the case of neutrons, nobody has ever observed GQS of atoms and antiatoms. GQS and a related phenomenon of Centrifugal Quantum States (CQS) of these particles is a sensitive method for the searches for extra short-range forces arising due to yet undiscovered light bosons or other phenomena beyond the Standard Model, manifestations of extra dimensions or dark matter. The techniques developed within GQS studies promise to help achieving ultralow energies of H thus providing unprecedented conditions for optical and hyperfine spectroscopy of H with ultimate precision, which will be pursuit within the GRASIAN project.
Science Division
Institute Laue-Langevin (ILL)
Grenoble, France
Research Profile
Abstract:
Gravitational quantum states (GQS) are traps for ultracold massive particles with gravity on top and a specularly reflecting mirror with a sharply changing surface potential on bottom. Ultralow energies make this system very sensitive to any tiny interactions and large sizes simplify the experimental techniques. GQS was discovered in experiments with ultracold neutrons (UCN) in 2002 and since then, they are actively used by several research groups (qBounce, Tokyo, GRANIT) at ILL, Grenoble.
While repulsive neutron-nuclei optical potential of many materials totally reflect UCN from surfaces, attractive van der Waals/Casimir-Polder potentials can also reflect ultracold atoms and molecules at surface due to quantum reflection. In contrast to the case of neutrons, nobody has ever observed GQS of atoms and antiatoms. GQS and a related phenomenon of Centrifugal Quantum States (CQS) of these particles is a sensitive method for the searches for extra short-range forces arising due to yet undiscovered light bosons or other phenomena beyond the Standard Model, manifestations of extra dimensions or dark matter. The techniques developed within GQS studies promise to help achieving ultralow energies of H thus providing unprecedented conditions for optical and hyperfine spectroscopy of H with ultimate precision, which will be pursuit within the GRASIAN project.
Ms. Lisa Hunter and Mr. Rafael Palomino
Institute for Scientist and Engineer Educators (ISEE)
University of California Santa Cruz
Santa Cruz, California
Speaker Profile - Lisa Hunter
Abstract:
The Institute for Scientist and Engineer Educators (ISEE) has been working with the science, technology, engineering, and mathematics (STEM) community since 2001 to prepare early-career scientists and engineers to become effective and inclusive in their teaching and mentoring. At the heart of this work is the Professional Development Program (PDP), which provides graduate students and postdocs intensive training in teaching methods supported by research and a practical teaching experience with students at the undergraduate level. More than 550 participants have now completed the program and have used the experience to obtain jobs, fellowships, and grants. Participants become part of an enduring national community of scientists and engineers dedicated to effective and inclusive education. ISEE was recently awarded a grant from the NSF, "Advancing Inclusive Leaders in Astronomy," with an NSF physics supplement, which provides support for graduate students and postdocs at ISEE chapters to participate in the PDP and for alumni at sites across the U.S. to lead and expand upon ISEE's prior work at their own institutions. This presentation will include information about the PDP, including research projects related to PDP thematic elements and how they increase student performance in the classroom.
The University of South Carolina is ISEE's newest chapter, currently operating in the Physics and Astronomy department with Chapter Lead and PDP alumnus, Steven Rodney. The USC chapter will send at least one new team to the PDP in Spring 2019 and we are actively seeking student and postdoc participants as well as faculty partners.
Institute for Scientist and Engineer Educators (ISEE)
University of California Santa Cruz
Santa Cruz, California
Speaker Profile - Lisa Hunter
Abstract:
The Institute for Scientist and Engineer Educators (ISEE) has been working with the science, technology, engineering, and mathematics (STEM) community since 2001 to prepare early-career scientists and engineers to become effective and inclusive in their teaching and mentoring. At the heart of this work is the Professional Development Program (PDP), which provides graduate students and postdocs intensive training in teaching methods supported by research and a practical teaching experience with students at the undergraduate level. More than 550 participants have now completed the program and have used the experience to obtain jobs, fellowships, and grants. Participants become part of an enduring national community of scientists and engineers dedicated to effective and inclusive education. ISEE was recently awarded a grant from the NSF, "Advancing Inclusive Leaders in Astronomy," with an NSF physics supplement, which provides support for graduate students and postdocs at ISEE chapters to participate in the PDP and for alumni at sites across the U.S. to lead and expand upon ISEE's prior work at their own institutions. This presentation will include information about the PDP, including research projects related to PDP thematic elements and how they increase student performance in the classroom.
The University of South Carolina is ISEE's newest chapter, currently operating in the Physics and Astronomy department with Chapter Lead and PDP alumnus, Steven Rodney. The USC chapter will send at least one new team to the PDP in Spring 2019 and we are actively seeking student and postdoc participants as well as faculty partners.
Dr. Sylvester Ekpenuma, Professor
School of Natural Sciences and Mathematics
Claflin University
Orangeburg, South Carolina
Research Profile
School of Natural Sciences and Mathematics
Claflin University
Orangeburg, South Carolina
Research Profile
Abstract:
Defects and impurities in materials affect their properties. For semiconductors, these can significantly affect their electronic and structural properties. Given their usefulness in device applications, there has been extensive research in defects and impurities in semiconductors in order to better understand various phenomena associated with their use. Experimental identification and characterization are challenging as defects sometimes develop even in the best experimental conditions. Theoretical modeling has emerged as a needed complement to experimental work and computational advances have led to reasonable and accurate results that can serve as predictive tools for defect identifications. This presentation will review some theoretical defect modeling techniques and apply the special quasi-random structures approach for the study of defects in cadmium zinc telluride.
Defects and impurities in materials affect their properties. For semiconductors, these can significantly affect their electronic and structural properties. Given their usefulness in device applications, there has been extensive research in defects and impurities in semiconductors in order to better understand various phenomena associated with their use. Experimental identification and characterization are challenging as defects sometimes develop even in the best experimental conditions. Theoretical modeling has emerged as a needed complement to experimental work and computational advances have led to reasonable and accurate results that can serve as predictive tools for defect identifications. This presentation will review some theoretical defect modeling techniques and apply the special quasi-random structures approach for the study of defects in cadmium zinc telluride.
Dr. Arthur Hebard
Distinguished Professor of Physics
Member of the National Academy of Sciences
University of Florida
Gainesville, FL
Research Profile
Distinguished Professor of Physics
Member of the National Academy of Sciences
University of Florida
Gainesville, FL
Research Profile
Abstract:
The crystalline layered high-Tc superconductor Bi-2212 can be easily cleaved into
smoothly faceted flakes, which, when placed into intimate physical contact with a
variety of layered materials or bulk semi-conductors, form heterogeneous junctions.
Two such junctions are discussed in this talk. Bi-2212/1T-TAS2, the 1T-TaS2 is a
Mott insulator harboring charge density waves (CDWs) and Bi-2212/n-GaAs Schottky barrier
junctions, which manifest quantum mechanical tunneling at low bias voltages. The
CDW order in the 1T-TaS2 appears to play an important role by coexisting with an unexpected
and surprisingly high Tc of the induced proximity gap which, for junctions with high
transparencies, is seen to have a surprisingly large value (~ 20 meV) equal to half
that of intrinsic Bi-2212 (~ 40 meV). Proximity-induced high-Tc superconductivity
in the 1T-TaS2 is driven by coupling to the metastable metallic phase coexisting within
the Mott commensurate (CCDW) phase and associated with a concomitant change of the
CCDW order parameter in the interfacial region. For the Bi-2212/n-GaAs Schottky barrier
junctions, modifications to the thermionic emission equation provide an excellent
description of the I-V characteristics even at low temperatures where tunneling is
found by differential conductance spectroscopy measurements to be important and capacitance
measurements under reverse bias suggest an unexpectedly long electric field screening
length in the superconductor.
Dr. Marco Ajello, Assistant Professor
Abstract:
The light emitted by all galaxies across the history of the Universe is encoded in
the intensity of the extragalactic background light (EBL), the diffuse cosmic radiation
field at ultraviolet, optical, and infrared wavelengths. The EBL is a source of opacity
for high-energy γ rays via the photon-photon interaction (γγ --> e+e-), leaving a
characteristic attenuation imprint in the spectra of distant γ-ray sources.
In this talk, I will report on unprecedented measurement of the EBL using data from
the Large Area Telescope on board of Fermi, which has allowed us to measure the star-formation
history and the density of faint galaxies during the re-ionization.
Dr. Luca Guazzotto, Associate Professor
Department of Physics
Auburn University
Auburn, Alabama
Research Profile
Department of Physics
Auburn University
Auburn, Alabama
Research Profile
Abstract:
Nuclear fusion energy production has been the ultimate goal of an active field of
research for several decades. In addition to the technological and physics challenges
that need to be overcome to achieve fusion energy production, some considerations
at a macroscopic level are also necessary. In particular, a precise energy balance
needs to be satisfied in order to achieve net energy production. The so-called "Lawson
criterion," derived from the original work by Lawson in 1957, has been for decades
the de-facto standard of our understanding of energy balance in nuclear fusion reactors
and experiments.
In this talk, we will review the basis for energy balance and power production in
fusion devices and discuss the details of the Lawson criterion. In the last part
of the talk, we will highlight some of the recent improvement and extensions to the
Lawson criterion that will allow us to gain a better understanding of the requirements
for fusion energy production.
Dr. Pawel Mazur, Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
I will talk about superfluid universe, the ground state in quantum gravity, and gravastars. Quantum mechanical considerations applied to the largest physical system in evidence have led to the understanding that there must exist such a thing as vacuum energy, which in its ground state should be homogeneous and isotropic, but in the presence of "impurities" (baryons), it will exhibit inhomogeneities. Superfluid is a condensate. Considering droplets of such a condensate, one arrives at the concept of a gravastar, the maximally supercompact material configuration consistent with the laws of gravitation. It just happens that such objects are abundant in the Universe. There is one in the Center of the Milky Way galaxy known as the Sag A*, which has a mass of approximately 4.4 million Solar masses. The Event Horizon Telescope (EHT), a planet-wide array of radio telescopes, will either refute or confirm predictions following from the gravastar theory of super-compact objects in our Universe in the next few years.
I will talk about superfluid universe, the ground state in quantum gravity, and gravastars. Quantum mechanical considerations applied to the largest physical system in evidence have led to the understanding that there must exist such a thing as vacuum energy, which in its ground state should be homogeneous and isotropic, but in the presence of "impurities" (baryons), it will exhibit inhomogeneities. Superfluid is a condensate. Considering droplets of such a condensate, one arrives at the concept of a gravastar, the maximally supercompact material configuration consistent with the laws of gravitation. It just happens that such objects are abundant in the Universe. There is one in the Center of the Milky Way galaxy known as the Sag A*, which has a mass of approximately 4.4 million Solar masses. The Event Horizon Telescope (EHT), a planet-wide array of radio telescopes, will either refute or confirm predictions following from the gravastar theory of super-compact objects in our Universe in the next few years.
Dr. Frank Avignone, III, Carolina Endowed Professor of Physics and Astronomy
Department of Physics and Astronomy
University of South Carolina
Research Profile
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The discovery that there was far more mass in galaxies than contained in visible material
was made by Fritz-Zwicky in 1933. He drew this conclusion by observing the motions
of galaxies in the Coma Cluster and by applying the virial theorem. He concluded
that there was several hundred times more mass in the Cluster than could be accounted
for by the mass in stars and dust. He called this unobserved mass "Dunkel Materie"
in his native Bulgarian language. Following the publication of his results, there
were a number of other observations that clearly support this conclusion. We will
review the other observations and then discuss the history of the experimental direct
searches from the first one published in 1986, to the many efforts ongoing today.
In particular, the roles played by members of the USC Department of Physics and Astronomy
in the past and present experiments will be discussed.
Dr. Nahum Arav, Professor
Department of Physics
Virginia Polytechnic Institute
Blacksburg, Virginia
Research Profile
Department of Physics
Virginia Polytechnic Institute
Blacksburg, Virginia
Research Profile
Abstract:
Quasar outflows are a prime candidate for producing various galactic-scale feedback
processes: explaining the relationship between the masses of the central black hole
and the galaxy's bulge, and chemically enriching the Intra-cluster medium. Using
the Hubble Space Telescope, we observed the first sample of quasar outflows that covers
the 500-1050 Angstrom rest-frame spectral region (XUV). These observations are revolutionizing
our understanding of the outflows and their influence on the host galaxy. XUV coverage
is the only way to probe the very high ionization phase that carries 90% or more of
the outflowing material, and obtain the distances of each outflow from the central
source. The survey uncovered three outflows, which are likely to have the largest
outflow kinetic-luminosity measured to date.
Dr. Yordanka Ilieva, Associate Professor
Department of Physics and Astronomy
University of South Carolina
Research Profile
Research Profile
Abstract:
Gluons mediate the strong interaction that binds visible matter and, together with
quarks, are the building blocks of all hadrons. Thus, the study of gluons is of fundamental
importance for understanding the strong dynamics that gives protons, neutrons, and
nuclei their basic properties. Among the gauge bosons in the Standard Model, gluons
are the only self-interacting particles. The gluon self-interaction causes effects
that are unique for strongly-interacting matter and are not observed in electroweak
phenomena. One such effect is confinement, meaning that no single quark or gluon
can be observed in isolation. The practical experimental consequence of confinement
is that one cannot break a proton or a neutron into quarks and gluons and study these
constituents directly. Special imaging techniques need to employed in order to construct
the three-dimensional maps of gluons in nucleons and nuclei and to explore the interactions
between gluons and their contribution to the nucleon-nucleon force. While deep inelastic
inclusive reactions have been instrumental to study the longitudinal momentum distributions
of gluons, the measurements of certain exclusive nuclear reactions allow to obtain
information about how the gluons are distributed in space in a plane perpendicular
to the parent nucleon or nucleus motion.
In this talk, we will present a program that is being carried out at Jefferson Lab
to study the transverse gluon structure of proton, neutron, and deuteron in fixed-target
experiments. This is accomplished by scattering a photon beam off a fixed proton
or deuteron target and detecting in coincidence an outgoing intact proton or deuteron
and a J/y meson. We will also discuss high-precision gluon imaging planned with the next large
U.S. nuclear-physics installation, the Electron-Ion Collider (EIC).
Dr. Robin Shelton, Professor
Abstract:
Sensitive observations have found enormous clouds of material beyond our Milky Way Galaxy. Some are as large as mini-galaxies with as much mass as 100 million Suns. Others are shreds that were ripped from nearby galaxies. Additional observations show that several nearby clouds are currently interacting with our own Galaxy. Some have reportedly shot through the Milky Way's disk while others are currently passing through the less dense outskirts of our Galaxy. My group has been computationally modeling these clouds, called high velocity clouds (HVCs), in order to determine how they affect our Galaxy and how our Galaxy affects them.
In this presentation, I will show how HVCs behave on timescales of hundreds of millions of years, how they shed streamers of highly ionized gas that become incorporated into our Galaxy, and what happens when they collide with the dense gas in our Galaxy's disk.
Sensitive observations have found enormous clouds of material beyond our Milky Way Galaxy. Some are as large as mini-galaxies with as much mass as 100 million Suns. Others are shreds that were ripped from nearby galaxies. Additional observations show that several nearby clouds are currently interacting with our own Galaxy. Some have reportedly shot through the Milky Way's disk while others are currently passing through the less dense outskirts of our Galaxy. My group has been computationally modeling these clouds, called high velocity clouds (HVCs), in order to determine how they affect our Galaxy and how our Galaxy affects them.
In this presentation, I will show how HVCs behave on timescales of hundreds of millions of years, how they shed streamers of highly ionized gas that become incorporated into our Galaxy, and what happens when they collide with the dense gas in our Galaxy's disk.
Dr. Vincente Guiseppe, Assistant Professor
Department of Physics and Astronomy
Department of Physics and Astronomy
Abstract:
Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton number violating process, and the effective Majorana neutrino mass. The MAJORANA Collaboration is operating its DEMONSTRATOR array of high-purity Ge detectors at the Sanford Underground Research Facility in South Dakota to search for neutrinoless double-beta decay in (76)Ge. A similar experiment by the GERDA collaboration is operating at LNGS in Italy. The first results from the MAJORANA DEMONSTRATOR's initial 10 kg-yr of exposure has set a half-life limit on the decay while an upcoming release of the unblinded data set is planned to reach 30 kg-yr of exposure. The MAJORANA DEMONSTRATOR and GERDA experiments have achieved the lowest backgrounds and a superior energy resolution at the neutrinoless double-beta decay region of interest. These results demonstrate that (76)Ge is an ideal isotope for a large next generation experiment. Building on the successes of the MAJORANA DEMONSTRATOR and GERDA, the LEGEND collaboration has been formed to pursue a ton-scale (76)Ge experiment. This talk will present the initial results from the MAJORANA DEMONSTRATOR' experiment, the plan for the LEGEND experiment, and the role the USC group is playing in the overall (76)Ge program.
Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton number violating process, and the effective Majorana neutrino mass. The MAJORANA Collaboration is operating its DEMONSTRATOR array of high-purity Ge detectors at the Sanford Underground Research Facility in South Dakota to search for neutrinoless double-beta decay in (76)Ge. A similar experiment by the GERDA collaboration is operating at LNGS in Italy. The first results from the MAJORANA DEMONSTRATOR's initial 10 kg-yr of exposure has set a half-life limit on the decay while an upcoming release of the unblinded data set is planned to reach 30 kg-yr of exposure. The MAJORANA DEMONSTRATOR and GERDA experiments have achieved the lowest backgrounds and a superior energy resolution at the neutrinoless double-beta decay region of interest. These results demonstrate that (76)Ge is an ideal isotope for a large next generation experiment. Building on the successes of the MAJORANA DEMONSTRATOR and GERDA, the LEGEND collaboration has been formed to pursue a ton-scale (76)Ge experiment. This talk will present the initial results from the MAJORANA DEMONSTRATOR' experiment, the plan for the LEGEND experiment, and the role the USC group is playing in the overall (76)Ge program.
Dr. Yanwen Wu, Assistant Professor
Department of Physics and Astronomy
Department of Physics and Astronomy
Abstract:
Our universe is made up of particles ranging from the fundamental few, such as quarks, to a vast sea of composites and quasiparticles, such as atoms and excitons. While there is still much to uncover on the fundamental level, properties of particles in the composite realm are well-identified and better understood because their interaction is mediated by the ubiquitous photon. This knowledge provides researchers in the fields of atomic and condensed matter the tools to create and manipulate quasiparticles with a high degree of precision and versatility.
In this talk, I will discuss the properties of two specific types of quasiparticles (excitons and surface plasmon polaritons) in two different condensed matter systems (semiconductor and metal) and how they can be optically measured and manipulated for potential applications in quantum information processing and nanoscale photonic circuitry.
Our universe is made up of particles ranging from the fundamental few, such as quarks, to a vast sea of composites and quasiparticles, such as atoms and excitons. While there is still much to uncover on the fundamental level, properties of particles in the composite realm are well-identified and better understood because their interaction is mediated by the ubiquitous photon. This knowledge provides researchers in the fields of atomic and condensed matter the tools to create and manipulate quasiparticles with a high degree of precision and versatility.
In this talk, I will discuss the properties of two specific types of quasiparticles (excitons and surface plasmon polaritons) in two different condensed matter systems (semiconductor and metal) and how they can be optically measured and manipulated for potential applications in quantum information processing and nanoscale photonic circuitry.
Dr. Dean Lee, Professor
Department of Physics and Astronomy
Department of Physics and Astronomy
Abstract:
This is an introduction to how atomic nuclei and other quantum few- and many-body systems can be studied using lattice simulations. The first part of the talk explains the basic formalism called lattice effective field theory. The rest of the talk is a discussion of novel methods and the new physics insights one gains with each. The methods discussed are the adiabatic projection method for scattering and reaction calculations, pinhole algorithm for probing structure and thermodynamic properties, and eigenvector continuation for extending calculations to regions of parameter space where things otherwise break down.
This is an introduction to how atomic nuclei and other quantum few- and many-body systems can be studied using lattice simulations. The first part of the talk explains the basic formalism called lattice effective field theory. The rest of the talk is a discussion of novel methods and the new physics insights one gains with each. The methods discussed are the adiabatic projection method for scattering and reaction calculations, pinhole algorithm for probing structure and thermodynamic properties, and eigenvector continuation for extending calculations to regions of parameter space where things otherwise break down.
Prof. Sergey Alekhin
Deutsches-Elektronen-Synchrotron (DESY)
University of Hamburg
Institute for High-Energy Physics
Hamburg, Germany and Protvino, Russia
Research Profile
University of Hamburg
Institute for High-Energy Physics
Hamburg, Germany and Protvino, Russia
Research Profile
Abstract:
Results of the QCD analysis of a variety of the hard-scattering data is over viewed
with a particular focus on determination of the quark distributions in the nucleon.
A potential of the recent precise data collected at the Large Hadron Collider (LHC)
for the problem of quark species disentangling is discussed and compared to the impact
of the low-energy fixed-target data alongside of modeling the heavy-quark contribution
within various factorization schemes. Finally, remaining challenges and potential
improvements in the field are outlined.
Dr. Joseph E. Johnson
Distinguished Professor Emeritus
Department of Physics and Astronomy
University of South Carolina
Research Profile
Research Profile
Abstract:
For over 100 years, the dominant problem in theoretical physics has been the lack
of integration of the theory of general relativity (GR) with quantum theory (QT) and
the standard model (SM). QT and the SM are built upon a non-commuting operator (Lie) algebra of fundamental
observables for position, momentum, energy, angular momentum, charge, strangeness
and other observables for describing atomic and nuclear level phenomena. This algebra expresses the interference in the order of fundamental measurements.
But GR is framed as nonlinear differential equations for the curved metric of space-time in a Riemannian Geometry
(RG) without an operator algebra for its fundamental observables of space-time and
of the metric.
It will be shown that the Einstein equations for GR as well as the underlying RG and
can be reformulated as a generalized Lie algebra with a single assumption that generalizes
the space-time metric to be a function of the position operators from quantum theory.
Since the metric is now an operator, this approach generalizes the framework of the
underlying Heisenberg Lie algebra and consequently the Lorentz and Poincare algebras
when gravitation is dominant. The proposed integrated algebraic system is shown
to give exactly the Einstein equations with large masses and dominant gravity (small
h) and likewise to exactly give traditional QT and the SM frameworks when gravity
is negligible. Possible observable tests of this proposed integration and new results
are discussed. This approach also admits extensions to extra dimensions as with string
theories. However, some of the core problems of such an integration (renormalization,
covariant GR gauge transformations and their merger with the SM Yang Mills theory)
are not yet solved. The presentation will end with a purely mathematical derivation
of the foundations of RG based upon a generalized Lie algebra.
Dr. Alessandro Pilloni
Theory Center Postdoctoral Staff
Thomas Jefferson National Accelerator Facility
Newport News, Virginia
Research Profile
Research Profile
Abstract:
Although QCD is universally acknowledged as the theory of strong interactions, the
way how the fundamental degrees of freedom (quark and gluons) arrange themselves into
the observed hadrons is still a mystery. Moreover, the presence of multiple states leads to intricate interference patterns
that make the extraction of meaningful information challenging.
In this colloquium, I will discuss the role of amplitude analysis in converting the
ra experimental data into robust physics information. I will finally present some of the phenomenological models used to describe the
features of the spectrum.
Dr. David B. Tanner, Professor
Department of Physics
University of Florida
Gainesville, Florida
Research Profile
Research Profile
Abstract:
The Axion Dark Matter eXperiment (ADMX) is conducting a search for axions within the
dark-matter halo of our Galaxy. The nature of the dark matter in the Universe, one of the most compelling questions
in all of science, will be clarified by the results of this search. Dark matter makes up roughly 85% of the mass in the universe and we don’t know what
it is. It interacts extremely weakly with the ordinary matter and energy in the universe,
making detection very challenging. Axions are a very well-motivated candidate for the dark matter. Many would say these days that they are the best-motivated candidate. Axions can be detected by their conversion to microwave photons in a strong magnetic
field; this process is the basis of many searches for axions and axion-like particles.
The ADMX experiment employs a large-volume superconducting magnet, a high-Q tunable
microwave cavity, an ultrasensitive SQUID microwave amplifier, and a high-performance
dilution refrigerator to enable 100 mK temperatures for cavity and SQUID. In the
last year, this “Generation 2” ADMX detector has reached the sensitivity to detect
axions even in the case where they are as weakly coupled as theory allows. The ADMX
detector, located at the University of Washington, has just completed its first run
at this design sensitivity. There were no detections and the search continues with
a second science run. The resulting limits on axion mass, the prospects for the ongoing
search, and the outlook for the future will be discussed.
Dr. Andrew B. Greytak, Assistant Professor
Department of Chemistry and Biochemistry
University of South Carolina
Research Profile
Research Profile
Abstract:
The behavior of 0, 1, and 2-dimensional nanoscale materials is strongly influenced
by surface structure that is subject to exchange with the surrounding environment.
Analysis of the surfaces of materials of different dimensionalities can require considerably
different approaches, but common to all are shared concepts of charge balance, coordination
chemistry, and crystallography; and shared goals and challenges in developing scalable
approaches to sensors and optoelectronic devices. In this talk, I will focus on two
areas of ongoing research in our lab.
In the first area, we are developing gel permeation chromatography as a multifunctional
processor for purification and ligand exchange chemistry of a variety of compound
semiconductor nanocrystals, including fluorescent quantum dots (QDs). GPC serves as
a valuable tool in preparing ligand-exchanged quantum dots with diverse functions
including water solubility, and in providing a well-defined initial state for thermodynamic
investigations. I will emphasize the use of GPC to study ligand exchange through on-column
reactions between QDs and small molecules. I will also discuss nascent efforts to
improve understanding and performance of assembled QD films (nanocrystal solids) as
solution-processable semiconductor materials.
In the second area, we are using functional imaging to study ligand association to
semiconductor nanowires, host-guest interactions in 1D microporous crystals, and optoelectronic
properties of epitaxial graphene/silicon carbide (EG/SiC)-based nanoelectronic heterostructures.
I will emphasize recent results from scanning photocurrent microscopy on EG/SiC bipolar
phototransistors.
Dr. Ronald D. Edge
Distinguished Professor Emeritus
Department of Physics and Astronomy
University of South Carolina
Research Profile
Distinguished Professor Emeritus
Department of Physics and Astronomy
University of South Carolina
Research Profile
Abstract:
The Cavendish Lab, my old haunt, recently informed me that they were building their
third generation. Since I am of the first generation founded in 1871, I had better
hurry up and tell about it. My friend, GFC Searle, knew Clerk Maxwell, the first
professor, personally. Maxwell was very humorous, unlike his picture. Searle also
founded the V2 V Club. I went there just after the war, when there was no heat. Taking
notes while wearing woolly gloves is not easy, even if lectures were from Bragg, Dirac,
and Hartree (using the Schroedinger approach). My research employed the 1 MeV Philips
Cockcroft-Walton accelerator, which looked like something from Frankenstein and worked
like that too.
Going to Australia in 1954, I re-built the Harwell electron synchrotron at the new Australian National University for photodisintegration.
Coming to USC in 1958, the department was converting from a teachers' training college to a research institution. Unfortunately, the new department head had died in the summer, Tony French had inherited the job, and he invited me. We commenced a Ph.D. program that year and acquired two graduate students. Theorists may only require pencil and paper, but experimentalists are more demanding. The NSF gave us funds for research on cosmic ray neutrons, and a small accelerator, for which the state provided a building. The first summer, the entire department camped there as it was the only building where air conditioning was available. USC had an enrollment of 3,000 students at the time, which has now increased to approximately 50,000 between all state campuses.
Going to Australia in 1954, I re-built the Harwell electron synchrotron at the new Australian National University for photodisintegration.
Coming to USC in 1958, the department was converting from a teachers' training college to a research institution. Unfortunately, the new department head had died in the summer, Tony French had inherited the job, and he invited me. We commenced a Ph.D. program that year and acquired two graduate students. Theorists may only require pencil and paper, but experimentalists are more demanding. The NSF gave us funds for research on cosmic ray neutrons, and a small accelerator, for which the state provided a building. The first summer, the entire department camped there as it was the only building where air conditioning was available. USC had an enrollment of 3,000 students at the time, which has now increased to approximately 50,000 between all state campuses.
Dr. Juan I. Collar, Professor
Kavli Institute for Cosmological Physics
University of Chicago
Chicago, Illinois
Research Profile
Kavli Institute for Cosmological Physics
University of Chicago
Chicago, Illinois
Research Profile
Abstract:
I will discuss the most recent results from PICO, a search for particle dark matter
using rather unconventional bubble chambers. I will then move on to COHERENT, an
ongoing effort at ORNL's Spallation Neutron Source seeking to exploit the recently-measured
coherent neutrino-nucleus scattering (CEvNS) as a new tool for neutrino physics.
The common ground between these two projects is the detection of keV and sub-keV nuclear
recoils. The challenges in developing and understanding detector technologies sensitive
to these will be emphasized.