Spring 2023 Colloquia

KATHRYN HAMILTON
Universtiy of Colorado @ Denver, Department of Physics

Abstract: Since their discovery in the late 1800’s, electrons have been a constant source of curiosity for scientists. Their properties and behaviour have been studied and harnessed to produce some of the greatest inventions of the past century, including electron microscopes and particle accelerators. However one fundamental question about their behaviour still remains: how do electrons move inside atoms and molecules?

Electron motion within atoms has proved difficult to study due to the incredibly short timescale it occurs on (the attosecond timescale, or 10^-18 seconds). One method of capturing electron motion is to use very short laser pulses to take a series of snapshots of the system. This requires laser pulses shorter than the duration of the dynamics we want to observe (similar to using a short flash on a camera to obtain an image of a fast-moving object). The means to do this have only become possible in the past decade with the advent of new ultrashort (less than 100 as) lasers, which have become feasible due to a process called high‐harmonic generation (HHG).

Harmonic generation occurs when an atom is exposed to a short laser pulse. Electrons are removed from the atom by the laser field, accelerated, and then recombine with the parent atom emitting high-energy harmonic light. This light can then be manipulated to produce the attosecond pulses required to image electronic motion. Analysis of the spectra produced by harmonic generation can also give an insight on the attosecond‐scale dynamics of electrons. An accurate theoretical description of high harmonic generation would therefore be extremely beneficial for the advancement of attoscience.

To this end, a world‐leading computational method, known as RMT (R‐Matrix with Time dependence), has been developed at Queen’s University Belfast to model accurately and efficiently the behaviour of electrons in many‐electron atoms. In this seminar I will present recent results obtained using the RMT method, firstly to treat high-harmonic generation in two-color laser fields, and then on applications of the attosecond pulses generated during the HHG process to measure ionization delays.

Figure 1: High-harmonic spectrum of neon atoms irradiated by a two-color (800nm + 400nm) laser field. The red “v” shapes are spectral caustics, formed by the coalescence of two or more electron trajectories in the same energy space.

Bio: Kathryn Hamilton is a new Assistant Professor at the University of Colorado Denver. Previously she was a Postdoctoral Research Scholar at Drake University in Des Moines, Iowa, where she worked alongside Prof. Klaus Bartschat on applying R-Matrix methods to treat a variety of atomic physics problems. She obtained her PhD in 2019 under the supervision of Dr. Andrew Brown and Prof. Hugo van der Hart at Queen’s University Belfast with a thesis entitled “R-Matrix calculations for ultrafast two-colour spectroscopy of noble gas atoms”. Her current research focusses on observing and controlling multielectron dynamics in atoms exposed to external laser fields, and electron collisions with atomic species. When she is not running code on supercomputers all over the world, she likes to play traditional Irish music and domesticate feral cats. Both activities produce very similar sounds.

For an example of her work, you can see the recent YouTube video https://youtu.be/fqNEhL3JBXA.

The development of structured ultrafast laser sources is a key ingredient to advance our knowledge about the fundamental dynamics of electronic and spin processes in matter. In particular, it has been widely recognized the relevance of ultrafast sources structured in their spin angular momentum (SAM, associated to the polarization of light) and orbital angular momentum (OAM, associated with the transverse phase profile, or vorticity of a light beam) to study chiral systems and magnetic materials in their fundamental temporal and spatial scales. In that scenario, structured coherent extreme-ultraviolet (EUV)/soft x-ray pulses are emerging as unique tools to drive strong field physics, particularly thanks to the new opportunities they provide in the highly nonlinear process of high harmonic generation (HHG) [1,2]. 

Cylindrical vector beams are paradigmatic examples of structured beams, being defined by topological parameters, such as the Poincaré index. It is known that the topology of vector beams is directly transferred to the high-order harmonics when HHG is driven in gas targets [3,4]. In this context, crystalline solids stand as particularly appealing targets in HHG due to their characteristic symmetries which imprint an anisotropic nonlinear response [5].

In this talk we will review several works that have triggered the field of ultrafast structured EUV pulses during the last decade. We will compare the interplay of light and matter topology in HHG in gases and in crystalline targets. In particular, our macroscopic simulations of HHG in graphene [6, 7] allows us to study how the symmetry of the anisotropic response of the target couples with the driver’s topology. This scenario opens the route towards high-order harmonic spectroscopy techniques based on the topology of the harmonic radiation [7].

[1] L. Rego, K. Dorney, N. Brooks, Q. Nguyen, C. Liao, J. San Román, D. Couch, A. Liu, E. Pisanty, M. Lewenstein, L. Plaja, H. Kapteyn, M. Murnane, C. Hernández-García, Science 364, eaaw9486 (2019).
[2] L. Rego, N. J. Brooks, Q. L. D. Nguyen, J. San Román, I. Binnie, L. Plaja, H. C. Kapteyn, M. M. Murnane, C. Hernández-García, Science Advances 8, eabj7380 (2022).
[3] C. Hernández-García et al., Optica, 4, 520 (2017).
[4] A. de las Heras,  A. Pandey, J. San Román, J. Serrano, E. Baynard, G. Dovillaire, M. Pittman, C. Durfee, L. Plaja, S. Kazamias, O. Guilbaud, C. Hernández-García, Optica 9, 71-79 (2022).
[5] Ó. Zurrón-Cifuentes, R. Boyero-García, C. Hernández-García, A. Picón, L. Plaja, Opt. Expr., 27, 7776-7786 (2019).
[6] R. Boyero-García, Ó. Zurrón-Cifuentes, L. Plaja, and C. Hernández-García,  Optics Express 29, 2488-2500 (2021).
[7] A. García-Cabrera,  R. Boyero-García, Ó. Zurrón-Cifuentes, J. Serrano, J. San Román, L. Plaja, C. Hernández-García,

Abstract: Harnessing the behavior of complex systems is at the heart of quantum technologies. Precisely engineered ultracold gases are emerging as a powerful tool for this task. In this talk I will explain how ultracold strontium atoms trapped by light can be used to create optical lattice clocks – the most precise timekeepers ever imagined. I am going to explain why these clocks are not only fascinating, but of crucial importance since they can help us to answer cutting-edge questions about complex many-body phenomena and magnetism, to unravel big mysteries of our universe and to build the next generation of quantum technologies.

Bio: Prof. Ana Maria Rey obtained her bachelor’s degree in physics in 1999 from the Universidad de los Andes in Bogota, Colombia. She pursued her graduate studies at the University of Maryland, College Park, receiving a Ph.D. in 2004. She then joined the Institute of Theoretical, Molecular and Optical Physics at the Harvard-Smithsonian Center for Astrophysics as a Postdoctoral Fellow from 2005 to 2008. She joined JILA, NIST and the University of Colorado Boulder faculty in 2008. She is currently a JILA and NIST fellow and a Professor Adjoint in the Department of Physics. Rey’s research focuses on how to control and manipulate ultra-cold atoms, molecules and trapped ions for use as quantum simulators of solid state materials and for quantum information and precision measurements. Rey’s recognition to her work include, among others a MacArthur Foundation Fellowship (2013) and the Blavatnik National Awards for Young Scientists (2019).

Abstract: Harnessing the behavior of complex systems is at the heart of quantum technologies. Precisely engineered ultracold gases are emerging as a powerful tool for this task. In this talk I will explain how ultracold strontium atoms trapped by light can be used to create optical lattice clocks – the most precise timekeepers ever imagined. I am going to explain why these clocks are not only fascinating, but of crucial importance since they can help us to answer cutting-edge questions about complex many-body phenomena and magnetism, to unravel big mysteries of our universe and to build the next generation of quantum technologies.

Bio: Prof. Ana Maria Rey obtained her bachelor’s degree in physics in 1999 from the Universidad de los Andes in Bogota, Colombia. She pursued her graduate studies at the University of Maryland, College Park, receiving a Ph.D. in 2004. She then joined the Institute of Theoretical, Molecular and Optical Physics at the Harvard-Smithsonian Center for Astrophysics as a Postdoctoral Fellow from 2005 to 2008. She joined JILA, NIST and the University of Colorado Boulder faculty in 2008. She is currently a JILA and NIST fellow and a Professor Adjoint in the Department of Physics. Rey’s research focuses on how to control and manipulate ultra-cold atoms, molecules and trapped ions for use as quantum simulators of solid state materials and for quantum information and precision measurements. Rey’s recognition to her work include, among others a MacArthur Foundation Fellowship (2013) and the Blavatnik National Awards for Young Scientists (2019).

ERIC MAYOTTE
Colorado School of Mines

Ultra-High-Energy cosmic rays (UHECRs) are the most energetic objects yet observed, and can have individual particle energies of 1020 eV. The field of physics which studies them is called astroparticle physics and it sits at the intersection of high-energy particle physics and multi-messenger astrophysics. The primary goals for this field of study are identifying the astrophysical mechanisms capable of accelerating particles to these extreme energies and leveraging UHECR to probe physics at energies far beyond what human made experiments are capable of producing in the near future.

Right now is an exciting time in astroparticle physics as practically all aspects of this field are undergoing a rapid evolution due to the availability of high-quality, high-statistics data-sets, advancing computational techniques, and revolutions in instrumentation design and scale [1]. A particularly exciting development is the advent of new analysis techniques which can map the particle universe at the highest energies using the composition of arriving cosmic rays. With this method, for the first time a composition dependent anisotropy in the UHECR sky has been identified and is approaching discovery status [2]. Furthermore, the anisotropy itself may be a significant driver of our understanding of the highest-energy extra-galactic systems, as its strength far surpasses those predicted with the most current astrophysical models [3].

This talk will give a brief overview of UHECR physics and where it is going over the next 20 years. Special attention is given to the technique of mapping the UHECR sky in terms of primary composition.

[1] A. Coleman, J. Eser, E. Mayotte, F. Sarazin, F. Schröder, D. Soldin, T. Venters et al., “Ultra-High-Energy Cosmic Rays: The Intersection of the Cosmic and Energy Frontiers,” Astroparticle Physics Special issue 147, 5 2022.
[2] E. Mayotte et al., “Indication of a mass-dependent anisotropy above 1018.7 eV in the hybrid data of the Pierre Auger Observatory,” PoS, vol. ICRC2021, p. 321, 2021.
[3] D. Allard, J. Aublin, B. Baret, and E. Parizot, “What can be learnt from UHECR anisotropies observations? Paper I : large-scale anisotropies and composition features,” 10 2021.

Biography: Dr. Eric Mayotte is a Mines physics alum, having received both his undergraduate and PhD in the Mines Physics department. He currently works in high-energy astrophysics looking at both cosmic rays and neutrinos. His PhD, under Professor Fred Sarazin, focused on searching for exotic matter by identifying low-velocity, high-energy, particle showers in the ultra-high-energy cosmic ray data collected by the Pierre Auger Observatory and was awarded best physics thesis at Mines in 2016. in 2016 he took a post-doc position under the spokesperson of the Pierre Auger Observatory, Professor Karl-Heinz Kampert at the University of Wuppertal in Wuppertal, Germany. During this post-doc, Eric developed a first of its kind method to map out the high-energy particle universe using the chemical composition of arriving cosmic ray primaries. This work has led to the first ever identification of a composition anisotropy in the flux of cosmic rays which is nearing discovery status, and was given a best contributed talk award at the largest international conference on astroparticle physics (ICRC). In August 2021, Eric returned to Mines as a post-doc to collaborate with Professor Fred Sarazin in order to build a micro-cosmic ray observatory in Utah and is working on the development of a space-based high-energy neutrino simulation suite in a collaboration with NASA scientists. When not working on physics, you’ll often find him skiing at A-Basin, playing cribbage at GCB, or reading a book at Higher Grounds.

Professor XIA HONG
University of Nebraska-Lincoln (UNL)
Department of Physics and Astronomy

Abstract: The heterointerfaces between ferroelectrics and 2D van der Waals (vdW) materials can be utilized to achieve novel interfacial coupling, nonvolatile field effect control, and nanoscale programmable functionalities. In this talk, I will discuss a range of emergent phenomena in ferroelectric/vdW heterostructures mediated by interfacial charge- and lattice-coupling. Combining polarization doping with nanoscale domain patterning enables local tuning of the carrier density in the vdW channel, which can lead to programmable Schottky junction states in MoS₂ [1]. This approach has also been exploited to create directional conducting paths in an insulating ReS₂ channel, which reveals that the conductivity ratio between the directions along and perpendicular to the Re-chain can exceed 5.5×10⁴ in monolayer ReS₂ [2]. Leveraging the interface-epitaxy between ferroelectric copolymer P(VDF-TrFE) and 1T’-ReS₂, we have fabricated large scale P(VDF-TrFE) thin films composed of highly ordered, close-packed, 10 and 35 nm wide crystalline nanowires [3]. We also observe an unconventional filtering effect of second harmonic generation signal resulting from the polar coupling of monolayer MoS₂ with either the polar domain or the chiral dipole rotation at the domain wall surface in ferroelectric oxide PbZr_0.2Ti_0.8O₃ [4]. Our study showcases the rich research opportunities offered by integrating ferroelectrics with 2D materials.

[1] Xiao et al., Phys. Rev. Lett. 118, 236801 (2017); Li et al., Nano Lett. 18, 2021 (2018).
[2] Li et al., Phys. Rev. Lett. 127, 136803 (2021).
[3] Li et al., Adv. Mater. 33, 2100214 (2021).
[4] Li et al., Nat. Commun. 11, 1422 (2020); Li et al., Adv. Mater., article No. 2208825 (2022).

Biography: Xia Hong is a Professor in the Department of Physics and Astronomy at the University of Nebraska-Lincoln (UNL). She received her B.S. degree from Peking University and Ph.D. from Yale University. After working as a postdoctoral scholar at the Pennsylvania State University, she joined the faculty of UNL in 2011 as an Assistant Professor. She received the NSF Career Award in 2012 and the DOE Early Career Award in 2016. Her research focuses on the nanofabrication, magnetotransport, and scanning probe studies of novel two-dimensional electron systems and complex oxide nanostructures and interfaces.

MANUEL CASTELLANOS BELTRAN
NIST

Abstract: Over the last two decades there has been tremendous interest in the advance of large-scale quantum computers. In particular, superconducting quantum processors has become the leading candidate for scalable quantum computing plat-form. Some of the initial research that paved the way for this field to take off was done at NIST several decades ago. In this talk I will give a summary of how my research in superconductive electronics group at NIST is helping solve some of the issues of scalability that plague this technology. I will also talk about my academic trajectory: my winding path from being an undergrad in Monterrey, Mexico, to a permanent staff scientist at NIST as well as discuss some of the challenges I’ve had in my scientific career.

Biography: Dr. Manuel Castellanos Beltran attended college in Mexico at the Monterrey Institute of Technology and Higher Education (Monterrey, NL.) where he received his BE in Engineering physics in 2003. He then attended the University of Colorado-Boulder where he earned his PhD in physics in 2010 working on developing Josephson parametric amplifiers for Quantum Information applications and quantum limited measurements under the guidance of Dr. Konrad Lehnert. Afterwards, he worked at Yale University as a Post-Doctoral Fellow (2010-2012) under Dr. Jack Harris where he studied persistent currents in normal metal mesoscopic rings using torque magnetometry techniques. Dr. Castellanos-Beltran then joined NIST as a PREP Post-Doctoral Fellow (2012-13) and NRC Post-Doctoral Fellow (2013-2015) working with Dr. Jose Aumentado studying low noise amplification with Josephson parametric amplifier for Qubit Readout. He is currently a researcher for the Superconductive Electronics Group working in the development of a high frequency arbitrary waveform synthesizer using cryogenic superconductive electronics for microwave metrology and quantum computing applications.

MANUEL CASTELLANOS BELTRAN
NIST

Abstract: Over the last two decades there has been tremendous interest in the advance of large-scale quantum computers. In particular, superconducting quantum processors has become the leading candidate for scalable quantum computing plat-form. Some of the initial research that paved the way for this field to take off was done at NIST several decades ago. In this talk I will give a summary of how my research in superconductive electronics group at NIST is helping solve some of the issues of scalability that plague this technology. I will also talk about my academic trajectory: my winding path from being an undergrad in Monterrey, Mexico, to a permanent staff scientist at NIST as well as discuss some of the challenges I’ve had in my scientific career.

Biography: Dr. Manuel Castellanos Beltran attended college in Mexico at the Monterrey Institute of Technology and Higher Education (Monterrey, NL.) where he received his BE in Engineering physics in 2003. He then attended the University of Colorado-Boulder where he earned his PhD in physics in 2010 working on developing Josephson parametric amplifiers for Quantum Information applications and quantum limited measurements under the guidance of Dr. Konrad Lehnert. Afterwards, he worked at Yale University as a Post-Doctoral Fellow (2010-2012) under Dr. Jack Harris where he studied persistent currents in normal metal mesoscopic rings using torque magnetometry techniques. Dr. Castellanos-Beltran then joined NIST as a PREP Post-Doctoral Fellow (2012-13) and NRC Post-Doctoral Fellow (2013-2015) working with Dr. Jose Aumentado studying low noise amplification with Josephson parametric amplifier for Qubit Readout. He is currently a researcher for the Superconductive Electronics Group working in the development of a high frequency arbitrary waveform synthesizer using cryogenic superconductive electronics for microwave metrology and quantum computing applications.

MATTHEW C. BEARD
Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE)
Chemical and Nanoscience Center, National Renewable Energy Laboratory, Golden, CO, USA

In this presentation I will discuss our studies of controlling the charge carrier dynamics, light/matter interactions, and spin populations in metal-halide organic/inorganic hybrid systems.

Lower dimensional perovskites are of particular interest since the lower degree of symmetry of the metal-halide connected octahedra and the large spin-orbit coupling can potentially lift the spin degeneracy. To achieve their full application potential, an understanding of spin-relaxation in these systems are needed. Here, we report an intriguing spin-selective excitation of excitons in a series of 2D lead iodide perovskite (n = 1) single crystals by using time- and polarization-resolved transient reflection spectroscopy. Exciton spin relaxation times as long as ~26 ps at low excitation densities and at room temperature were achieved for a system with small binding energy, 2D EOA₂PbI₄ (EOA=ethanolamine).

We have recently studied and developed a novel class of chiral hybrid semiconductors based upon layered metal-halide perovskite 2D Ruddlesden-Popper type structures.  These systems exhibit chiral induced spin selectivity (CISS) whereby only one spin sense can transport across the chiral layer and the other spin sense is blocked for one handedness of the chiral perovskite layer.  We show that chiral perovskite layers are able to achieve > 80% spin-current polarization.  We have also studied spin-injection from the chiral-layer to a non-chiral perovskite layer and find high spin-injection efficiency. We developed novel spin-based LEDs using non-chiral perovskite NCs as the light emitting layer that promotes light emission at a highly spin-polarized interface.  The LED spin-polarization is limited by spin-depolarization within the MHP NCs.

Finally, if time permits I will discuss our efforts for developing novel photocatalyst by combining the unique properties of metal-halide semiconductor nanocrystals with transition metals transition metal catalyst that is incorporated at the surface of the NCs. We show that such systems can drive multiple electron reactions.  These results demonstrate that the emergent properties of organic−inorganic hybrid systems offer unique opportunities in controlling light, charge and spin.

Bio: Matthew C. Beard is a Senior Research Fellow at the National Renewable Energy Laboratory and is Director of the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE) an Energy Frontier Research Center funded by the Office of Science within the US. Department of Energy. He is a fellow of the American Physical Society, the Royal Society of Chemistry, and AAAS. He received his Ph.D. in physical chemistry from Yale University in 2002. His research interest includes hot-carrier utilization (slowed hot-carrier cooling and multiple exciton generation), spin-to-charge conversion, quantum dots, metal-halide perovskites, and other reduced dimensional systems for solar energy transduction, photochemical energy conversion, and the use of ultrafast transient spectroscopies in tracking energy conversion processes.

MATTHEW C. BEARD
Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE)
Chemical and Nanoscience Center, National Renewable Energy Laboratory, Golden, CO, USA

In this presentation I will discuss our studies of controlling the charge carrier dynamics, light/matter interactions, and spin populations in metal-halide organic/inorganic hybrid systems.

Lower dimensional perovskites are of particular interest since the lower degree of symmetry of the metal-halide connected octahedra and the large spin-orbit coupling can potentially lift the spin degeneracy. To achieve their full application potential, an understanding of spin-relaxation in these systems are needed. Here, we report an intriguing spin-selective excitation of excitons in a series of 2D lead iodide perovskite (n = 1) single crystals by using time- and polarization-resolved transient reflection spectroscopy. Exciton spin relaxation times as long as ~26 ps at low excitation densities and at room temperature were achieved for a system with small binding energy, 2D EOA₂PbI₄ (EOA=ethanolamine).

We have recently studied and developed a novel class of chiral hybrid semiconductors based upon layered metal-halide perovskite 2D Ruddlesden-Popper type structures.  These systems exhibit chiral induced spin selectivity (CISS) whereby only one spin sense can transport across the chiral layer and the other spin sense is blocked for one handedness of the chiral perovskite layer.  We show that chiral perovskite layers are able to achieve > 80% spin-current polarization.  We have also studied spin-injection from the chiral-layer to a non-chiral perovskite layer and find high spin-injection efficiency. We developed novel spin-based LEDs using non-chiral perovskite NCs as the light emitting layer that promotes light emission at a highly spin-polarized interface.  The LED spin-polarization is limited by spin-depolarization within the MHP NCs.

Finally, if time permits I will discuss our efforts for developing novel photocatalyst by combining the unique properties of metal-halide semiconductor nanocrystals with transition metals transition metal catalyst that is incorporated at the surface of the NCs. We show that such systems can drive multiple electron reactions.  These results demonstrate that the emergent properties of organic−inorganic hybrid systems offer unique opportunities in controlling light, charge and spin.

Bio: Matthew C. Beard is a Senior Research Fellow at the National Renewable Energy Laboratory and is Director of the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE) an Energy Frontier Research Center funded by the Office of Science within the US. Department of Energy. He is a fellow of the American Physical Society, the Royal Society of Chemistry, and AAAS. He received his Ph.D. in physical chemistry from Yale University in 2002. His research interest includes hot-carrier utilization (slowed hot-carrier cooling and multiple exciton generation), spin-to-charge conversion, quantum dots, metal-halide perovskites, and other reduced dimensional systems for solar energy transduction, photochemical energy conversion, and the use of ultrafast transient spectroscopies in tracking energy conversion processes.

DEJI AKINWANDE
University of Texas @ Austin, Chandra Department of Electrical and Computer Engineering

Abstract: This presentation focuses on the discovery of memory effect in 2D atomically-thin nanomaterials towards greater scientific understanding and advanced engineering applications. Non-volatile memory devices based on 2D materials are an application of defects and is a rapidly advancing field with rich physics that can be attributed to vacancies combined with metal adsorption. In particular the talk will highlight our pioneering work on monolayer memory (atomristors) that has expanded to over a dozen 2D sheets and can enable various applications including zero-power devices, non-volatile RF switches, and memristors for neuromorphic computing. In addition, recent work on covid-19 biosensors will be presented towards exploiting quantum effects for improved sensitivity. Much of these research have been published in nature, advanced materials, and ACS journals.

References:
[1] M. Kim, G. Ducournau, S. Skrzypczak, S. J. Yang, P. Szriftgiser, N. Wainstein, K. Stern, H. Happy, E. Yalon, E. Pallecchi, and D. Akinwande, “Monolayer molybdenum disulfide switches for 6G communication systems,” Nature Electronics, 2022.
[2] R. Ge, X. Wu, L. Liang, …, J. C. Lee, and D. Akinwande, “A Library of Atomically Thin 2D Materials Featuring the Conductive-Point Resistive Switching Phenomenon,” Advanced Materials, vol. 33, 2021.
[3] S. M. Hus, R. Ge, P.-A. Chen, L. Liang, G. E. Donnelly, W. Ko, F. Huang, M.-H. Chiang, A.-P. Li, and D. Akinwande, “Observation of single-defect memristor in an MoS2 atomic sheet,” Nature Nanotechnology, 11/2020.
[4] S. Chen, M. R. Mahmoodi, … D. Akinwande, D. B. Strukov, and M. Lanza, “Wafer-scale integration of two-dimensional materials in high-density memristive crossbar arrays for artificial neural networks,” Nature Electronics, 10/2020.
[5] D. Akinwande, C. Huyghebaert, C.-H. Wang, Serna, S. Goossens, L. Li, H. S. P. Wong, and F. Koppens, “Graphene and 2D Materials for Silicon Technology,” Nature, 2019.

Biography: Deji Akinwande is an Endowed Full Professor at the University of Texas at Austin, and a Fellow of the IEEE and APS. He received the PhD degree from Stanford University in 2009. His research focuses on 2D materials and nanoelectronics/technology, pioneering device physics from lab towards applications. Prof. Akinwande has been honored with the 2019 Fulbright Specialist Award, 2017 Bessel-Humboldt Research Award, the U.S Presidential PECASE award, the inaugural Gordon Moore Inventor Fellow award, the inaugural IEEE Nano Geim and Novoselov Graphene Prize, the IEEE “Early Career Award” in Nanotechnology, the NSF CAREER award, several DoD Young Investigator awards, and was a past recipient of fellowships from the Kilby/TI, Ford Foundation, Alfred P. Sloan Foundation, 3M, and Stanford DARE. His research achievements have been featured by Nature news, Time and Forbes magazine, BBC, Discover magazine, Wall Street Journal, and many media outlets. He serves as an Editor for ACS Nano, and Nature NPJ 2D Materials and Applications.

RAMÓN BARTHELEMY
University of Utah, Physics and Astronomy

Abstract: Queer civil rights in the USA have been hard won from direct activism and organization of a diverse coalition of people, including trans women and men, People of Color, and members of the LGBT+ community more broadly. This talk will explore this history and take an in-depth look at how principles from this history were applied to physics to make significant policy changes. The data presented will uncover a concerning climate for LGBT+ physicists, which can be even more challenging for trans persons and People of Color.

Bio: Ramón Barthelemy is an assistant professor of physics and astronomy at the University of Utah and a fellow of the American Physical Society. Previous to his faculty position Ramón was a Fulbright Scholar in Finland, a Science Policy Fellow in the U.S. Department of Education and a private sector consultant. His work focuses on the lives, educational experiences, and career paths of marginalized students in physics and STEM. This has included work on LGBT+ people, graduate Students of Color, and women in physics. His work has been recognized with over $1M in National Science Foundation funding. Ramón was the 2020 recipient of the Fulbright Finland Alumni Award, the 2021 recipient of the AAPT Doc Brown Futures award, and the 2022 WEPAN Research award recipient. You can reach him on Twitter @RamonBarthelemy or his research group’s website www.PERUtah.com

Zoom

Abstract: Dirac semimetals are a recently discovered topological phase of quantum matter. α-Sn is unique among the Dirac semimetals because it is a single-element material and is therefore relatively easy to grow. Further, it can be transformed into other topological phases, such as a topological insulator or a Weyl semimetal, under strains or external fields. I will discuss our recent experimental work on α-Sn thin films along four directions:

1. Growth of α-Sn thin films by a CMOS-compatible sputtering technique.
2. Large damping enhancement in a ferromagnetic thin film due to the presence of topological surface states in an adjacent α-Sn thin film.
3. Current-induced magnetization switching via topological surface states in an α-Sn/Ag/CoFeB trilayer.
4. Spin-momentum-locking driven large magnetoresistance in α-Sn thin films that scales linearly with both magnetic and electric fields. These results indicate that topological Dirac semimetal α-Sn holds exciting promise of application in next-generation electronics and quantum technologies.

Biography: Mingzhong Wu received his Ph.D. in Solid State Electronics from Huazhong University of Science and Technology (China) in 1999, joined Colorado State University (CSU) in 2007, and is currently a Professor of Physics at CSU. His research interests include topological quantum materials, spintronics, magnetization dynamics, and nonlinear spin waves. He has authored over 170 technical papers and co-edited a major book on magnetic insulators. He served as an Editor for IEEE Magnetics Letters (2012- 2016) and is currently a Senior Editor for Journal of Alloys and Compound and an Editor for Physics Letters A. He served as the Education Committee Chair (2012-2015) and Finance Chair (2015-2018) of the IEEE Magnetics Society and is currently the Technical Committee Chair of the Society (since 2019). He was named “Professor Laureate” by the CSU College of Natural Sciences for 2019, 2020, and 2021. He was elected IEEE Fellow and APS Fellow in 2021.

MINGZHONG WU
Colorado State University, Department of Physics

Abstract: Dirac semimetals are a recently discovered topological phase of quantum matter. α-Sn is unique among the Dirac semimetals because it is a single-element material and is therefore relatively easy to grow. Further, it can be transformed into other topological phases, such as a topological insulator or a Weyl semimetal, under strains or external fields. I will discuss our recent experimental work on α-Sn thin films along four directions:

1. Growth of α-Sn thin films by a CMOS-compatible sputtering technique.
2. Large damping enhancement in a ferromagnetic thin film due to the presence of topological surface states in an adjacent α-Sn thin film.
3. Current-induced magnetization switching via topological surface states in an α-Sn/Ag/CoFeB trilayer.
4. Spin-momentum-locking driven large magnetoresistance in α-Sn thin films that scales linearly with both magnetic and electric fields. These results indicate that topological Dirac semimetal α-Sn holds exciting promise of application in next-generation electronics and quantum technologies.

Biography: Mingzhong Wu received his Ph.D. in Solid State Electronics from Huazhong University of Science and Technology (China) in 1999, joined Colorado State University (CSU) in 2007, and is currently a Professor of Physics at CSU. His research interests include topological quantum materials, spintronics, magnetization dynamics, and nonlinear spin waves. He has authored over 170 technical papers and co-edited a major book on magnetic insulators. He served as an Editor for IEEE Magnetics Letters (2012- 2016) and is currently a Senior Editor for Journal of Alloys and Compound and an Editor for Physics Letters A. He served as the Education Committee Chair (2012-2015) and Finance Chair (2015-2018) of the IEEE Magnetics Society and is currently the Technical Committee Chair of the Society (since 2019). He was named “Professor Laureate” by the CSU College of Natural Sciences for 2019, 2020, and 2021. He was elected IEEE Fellow and APS Fellow in 2021.