Rostock 2019 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 39: Ultrashort Laser Pulses
Q 39.9: Vortrag
Mittwoch, 13. März 2019, 16:15–16:30, S SR 211 Maschb.
Manifesting Berry phase in graphene without magnetic field — •Hamed Koochaki Kelardeh1, Alexandra Landsman1,2, Vadym Apalkov3, and Mark Stockman3 — 1Max Planck Institute for the Physics of Complex Systems, Dresden, Germany — 2Max Planck Postech, Pohang, Republic of Korea — 3Georgia State University, Atlanta, USA
We explore the coherent electron dynamics of graphene superlattices imposed on periodic nanowires, irradiated by a strong few-cycle circularly-polarized pulse. The conduction-band population distribution in the reciprocal space forms an interferogram with discontinuities related to the topological (Berry) fluxes at the Dirac points. One of the fundamental problems of topological physics of graphene is a direct observation of the Berry phase, which essentially requires self-referenced interferometry of electronic waves in the reciprocal space (PRB 93 (15), 155434). However, the Berry phase is ± π , and the self-referenced interferometry doubles it to ± 2π ; thereby avoiding any discontinuities in the interference fringes. Here we propose an approach to overtake this subtlety by coupling graphene to a nanowire superlattice. The Bragg scattering from the superlattices creates diffraction and "which way" interference in the reciprocal space reducing the Berry phase and making it directly observable in the electron interferograms without the involvement of the magnetic field.