Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session N32: Distinguished International Early Career Scientists in Quantum Physics (FIP, FECS)Invited Session Live Streamed
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Sponsoring Units: FIP FECS Chair: Maria Longobardi, University of Basel, Switzerland Room: McCormick Place W-183A |
Wednesday, March 16, 2022 11:30AM - 12:06PM |
N32.00001: Majorana bound states in topological insulators without a vortex Invited Speaker: Jelena Klinovaja In my talk, I will discuss topological phases in a three-dimensional topological insulator (TI) wire with a non-uniform chemical potential induced by gating across the cross-section [1]. This inhomogeneity in chemical potential lifts the degeneracy between two one-dimensional surface state subbands. A magnetic field applied along the wire, due to orbital effects, breaks time-reversal symmetry and lifts the Kramers degeneracy at zero-momentum. If placed in proximity to an s-wave superconductor, the system can be brought into a topological phase at relatively weak magnetic fields. Majorana bound states (MBSs), localized at the ends of the TI wire, emerge and are present for an exceptionally large region of parameter space in realistic systems. Unlike in previous proposals, these MBSs occur without the requirement of a vortex in the superconducting pairing potential, which represents a significant simplification for experiments. Our results open a pathway to the realisation of MBSs in present day TI wire devices. In the second part of my talk, I will switch from non-interacting systems, in which one neglects effects of strong electron-electron interactions, to interacting systems and, thus, to exotic fractional phases. In particular, I will focus on second-order TIs [2-7] and discuss two-dimensional fractional second-order topological superconductors, hosting zero-energy parafermion corner states. |
Wednesday, March 16, 2022 12:06PM - 12:42PM |
N32.00002: Variational Neural Annealing Invited Speaker: Estelle M Inack
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Wednesday, March 16, 2022 12:42PM - 1:18PM |
N32.00003: Electrically Switchable van der Waals Magnon Valves Invited Speaker: Jianhao Chen Van der Waals magnets have emerged as a fertile ground for the exploration of highly tunable spin physics and spin-related technology. Two-dimensional (2D) magnons in van der Waals magnets are collective excitation of spins under strong confinement. Although considerable progress has been made in understanding 2D magnons, a crucial magnon device called the van der Waals magnon valve, in which the magnon signal can be completely and repeatedly turned on and off electrically, has yet to be realized. Here we demonstrate such magnon valves based on van der Waals antiferromagnetic insulator MnPS3. By applying DC electric current through the gate electrode, we show that the second harmonic thermal magnon (SHM) signal can be tuned from positive to negative. The guaranteed zero crossing during this tuning demonstrates a complete blocking of SHM transmission, arising from the nonlinear gate dependence of the non-equilibrium magnon density in the 2D spin channel. Using the switchable magnon valves we demonstrate a magnon-based inverter. These results illustrate the potential of van der Waals anti-ferromagnets for studying highly tunable spin-wave physics and for application in magnon-base circuitry in future information technology. |
Wednesday, March 16, 2022 1:18PM - 1:54PM |
N32.00004: Imaging quasiparticle flow around electrostatic barriers in graphene using scanning tunneling potentiometry and Kelvin probe force microscopy Invited Speaker: Victor W Brar I will discuss how scanning tunneling potentiometry (STP) and Kelvin probe force microscopy (KPFM) can be used to quantify and image the electrochemical profile of graphene/hBN devices biased with in-plane currents. It will be shown how these measurements can reveal the profiles of in-plane electrostatic potentials, and to probe the local current density in the graphene sheet. By using an STM tip to draw electrostatic barriers, the flow profile of the quasiparticle current is investigated as it passes around circular barriers and through constrictions of different characteristic widths. I will show that for ballistic transport, the wavefunctions of carrier states can be directly imaged, revealing scattering states with novel properties. By increasing the sample temperature from 4.5K to 77K, it will be shown that the flow profile evolves in a manner that is consistent with a Knudsen-to-Gurzhi regime crossover, as the quasiparticles transition to a hydrodynamic phase. In particular, the conductivity of local constrictions is observed to exceed the ballistic limit, and localized charge accumulation/depletion is observed on the upstream/downstream side of barriers. |
Wednesday, March 16, 2022 1:54PM - 2:30PM |
N32.00005: Spins, microwaves and quantum technologies Invited Speaker: Jarryd J Pla Electron spin states in semiconductor chips and superconducting microwave electronics represent two leading platforms for emerging quantum technologies in the solid-state. Spins benefit from their atomic size and ultra-long coherence times, whilst superconducting microwave circuits are easy to manufacture and respond quickly to external stimuli. Both systems are considered front-running candidates for implementing large-scale quantum computers. I will present some of our key recent developments in both platforms, from demonstrating techniques to aid in the scaling of spin-based quantum processors [1,2], to new superconducting microwave amplifiers operating at the quantum noise limit [3]. I’ll also discuss what can be achieved when these two systems are brought together to form novel spin-superconductor hybrid devices with applications in spin resonance spectroscopy [4,5]. |
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