Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session V04: Dirac Electron Physics and Nanoscale Scanning Probes of Quantum Dynamics in Graphene: Atomic Defects, Topology and Geometry
2:30 PM–5:30 PM,
Thursday, March 8, 2018
LACC Room: 151
Sponsoring Units: DCMP DMP
Chair: Jairo Velasco, University of California, Santa Cruz
Abstract: V04.00002 : Berry phase jumps and giant nonreciprocity in Dirac quantum dots
3:06 PM–3:42 PM
Joaquin Rodriguez Nieva
Joaquin Rodriguez Nieva
Dirac electrons in 2D materials exhibit a Berry phase, an unusual feature induced by the pseudospin which causes the wave function to acquire a measurable phase when system parameters cycle around a closed path. Observing manifestations of the Berry phase via coherent control of quantum state trajectories is experimentally challenging in solid-state systems. In this talk, I will discuss our theoretical proposal to exploit confined Dirac electrons inside circular quantum dots to control and measure the Berry phase of electron orbital states. In particular, we show that weak magnetic fields can be used to control the behavior of electron trajectories and induce a giant non-reciprocal effect driven by the Berry phase. Non-reciprocity is manifest in anomalously large field-induced splittings of quantum dot resonances which are degenerate at B=0 due to time-reversal symmetry. The effect, which is strongest for gapless Dirac particles, overwhelms the magnetic-field-induced orbital and Zeeman splittings. This exotic behavior is unique to quantum dots in Dirac materials and is absent in conventional quantum dots. The non-reciprocity, predicted for a large family of two-dimensional Dirac materials, has recently been observed in scanning tunneling spectroscopy measurements in graphene. The effect is shown to be robust against perturbations of the circular confining potential and, as such, can be exploited in a variety of switchable optoelectronic applications.
 JFRN, L.S. Levitov, PRB 94, 235406 (2016).
 F. Ghahari, et al, Science 356, 845 (2017).
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