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HL: Fachverband Halbleiterphysik

HL 35: THz and MIR

HL 35.3: Talk

Wednesday, March 20, 2024, 15:30–15:45, EW 203

Mid-infrared photocurrents in topological insulator thin film — •Filippo Romano1,2, Holger Mirkes1,2, Nina Pettinger1,2, Alexander Holleitner1,2, and Christoph Kastl1,21Walter Schottky Institute and Physik-Department, Technical University of Munich, Germany — 2Munich Center for Quantum Science and Technology (MCQST), Munich, Germany

Clearly discriminating the transport of trivial bulk and non-trivial surface states remains often challenging in topological insulators because of their rather large residual bulk conductivity. Photogalvanic currents can serve as a tool to selectively address the surface states based on simple symmetry principles (Nanophotonics 2020, 9, 2693 - 2708). However, most experiments so far used a near-infrared excitation far above the fundamental bulk gap of the prototypical 3D topological insulators mixing surface and bulk states in the optical excitation process (Nat. Commun. 2015, 6, 6617). Here, we extend optoelectronic measurements of topological insulator thin films from near-infrared (from 0.8 µm) to mid-infrared wavelengths (up to 20 µm). The latter may allow a selective excitation of surface state photocurrents without contribution from bulk bands. The research is supported through the European Union’s Horizon Europe Research and Innovation Programme under Grant Agreement No 101076915 (2DTopS).

Keywords: Topological insulator; Photocurrent; Surface states; Photogalvanic effect

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