Regensburg 2025 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 21: Graphene: Electronic Structure and Excitations (joint session O/HL)
HL 21.2: Talk
Tuesday, March 18, 2025, 10:45–11:00, H6
Photocurrent control in a graphene-based Floquet topological insulator — •Weizhe Li1, Daniel Lesko1, Tobias Weitz1, Simon Wittigschlager1, Christian Heide1,2, Ofer Neufeld3, and Peter Hommelhoff1,4 — 1Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany — 2Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, USA — 3Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa, Israel — 4Department Physik, Ludwig-Maximilians-Universität München (LMU), 80799 München
Topological insulators offer unique opportunities for novel electronics and quantum phenomena. However, intrinsic material limitations often restrict their applications and practical implementation. A circularly-polarized laser pusle can generate topologically non-trivial non-equilibrium states known as Floquet topological insulators (FTIs) which host a variety of topological phenomena. Floquet engineering with strong optical fields opens routes to optically tunable band structures and devices for petahertz electronics.
Here we demonstrate coherent control of photocurrents in light-dressed graphene. Circularly-polarized laser pulses dress the graphene into an FTI, and phase-locked second harmonic pulses drive electrons in the FTI. This approach allows us to measure all-optical anomalous Hall currents and photocurrent circular dichroism, which put FTIs on equal footing with equilibrium topological insulators. The coherent control of photocurrents in graphene-based FTI connects optics tools to condensed matter physics.
Keywords: Floquet engineering; Topological insulator; Graphene