Bulletin of the American Physical Society
2020 Annual Meeting of the APS Four Corners Section (Virtual)
Volume 65, Number 16
Friday–Saturday, October 23–24, 2020; Albuquerque, NM (Virtual)
Session K01: Lustig Award SessionLive
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Chair: Kathrin Spendier, UCCS |
Saturday, October 24, 2020 9:30AM - 10:00AM Live |
K01.00001: Optically Controlling Femtosecond Hot Electron Currents in Nanoplasmonic Systems Invited Speaker: Jacob Pettine Plasmonic metal nanoparticles concentrate optical field energy into deeply sub-wavelength volumes, producing high densities of excited (hot) electrons and holes. While predicting and controlling the spatial and momentum distributions of these hot carriers remain significant challenges, such capabilities introduce exciting opportunities for actively controlling ultrafast currents in a variety of photocatalytic, photovoltaic, and nanoelectronic applications. Toward these ends, some recent insights from single-nanoparticle angle-resolved photoemission spectroscopy studies will be presented. Gold nanostars, for instance, behave as multi-tip photocathodes with simultaneous frequency- and polarization-selective tip hot spots for photocurrent directionality control. Gold nanorods, on the other hand, provide a unique testbed for distinguishing fundamental surface- vs. volume-mediated photoemission pathways and their corresponding hot electron spatial/momentum distributions. These investigations are complemented by a combination of classical finite element electrodynamics, semi-classical Monte Carlo, and fully quantum modeling for predictively understanding hot electron dynamics in arbitrary nanoplasmonic geometries. [Preview Abstract] |
Saturday, October 24, 2020 10:00AM - 10:30AM Live |
K01.00002: Precision Measurements of Parity Violation in Neutron-Nucleus Resonance States for Future Time-Reversal Violation Experiments Invited Speaker: Danielle Schaper The Standard Model of physics is the most complete, most robust, most well-tested theory in physics; it is our ‘rulebook’ which describes all of the known particles and their interactions. It is the culmination of the work of thousands of physicists over thousands of years and has been found to be an amazingly self-consistent theory. However, even with such an enthusiastic endorsement, we know that the Standard Model is not completely ‘correct.’ For one, it cannot presently explain many outstanding problems in physics, one of which is the baryon asymmetry of the Universe, or to put more simply: where did all of the matter that constitutes the Universe come from? And where is the antimatter? Nature adores symmetry. In the laboratory, for example, high-energy gamma rays can split into particle-antiparticle pairs in a process known as ‘pair production.’ But that’s just the thing–these reactions ALWAYS occur in particle-antiparticle pairs, and we have not yet seen any experimental evidence to the contrary. Therefore, it would seem that during the Big Bang, matter and antimatter should have been produced in exactly equal amounts. These matter-antimatter particle pairs would then collide and annihilate into photons, leaving almost nothing but a Universe made of radiation. But this is not what we see–we see a Universe made of matter. How can this be? In 1967, Andrei Sakharov proposed three conditions that, together, could explain the matter-antimatter asymmetry of the Universe: one of these conditions was the need for charge conjugation (C) symmetry and time-reversal (T) symmetry to be violated. The Neutron OPtics Time Reversal EXperiment (NOPTREX) collaboration seeks to find evidence of Tviolation in a system that has not yet been probed: resonant neutron-nucleus interactions of heavy nuclei. This talk will discuss the ideas behind the NOPTREX experiments as well as preliminary parity violation measurements that have been conducted at the Los Alamos Neutron Science CEnter (LANSCE). [Preview Abstract] |
Saturday, October 24, 2020 10:30AM - 11:00AM Live |
K01.00003: Theoretical studies of ultrafast imaging of electron dynamics in atoms Invited Speaker: Joel Venzke The development of ultrashort laser pulses with durations of a few tens of attoseconds (1 as = $10^{-18}$ s) has opened the possibility of observing and controlling the motion of electrons in matter at their natural time scale. However, the broad spectral bandwidth of the pulses pose the challenge that several linear and nonlinear pathways compete and interfere during the interaction of those pulses with the target. Experimental data, such as photoelectron angular distributions, which contain all the information about the amplitudes and phases of the initial electron wave packet describing the dynamics, are therefore difficult to analyze. Supported by results from perturbation theory and ab-initio numerical simulation, I will present the new theoretical tools I developed to identify the impact of individual transitions and interpret experimental observations. Furthermore, the new theoretical insights are used to propose experimental setups that probe electron dynamics such as reconstructing the motion of an electron wavepacket around an atomic nucleus. [Preview Abstract] |
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