Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 33: Poster Tuesday: Ultrafast Processes 2
O 33.2: Poster
Dienstag, 6. September 2022, 11:00–13:00, P3
High-harmonic generation from the surface state of Bi2Se3 with THz driving fields — •Tim Bergmeier, Suguru Ito, Jens Güdde, and Ulrich Höfer — Fachbereich Physik, Philipps-Universität Marburg, Germany
The acceleration of charge carriers through the Dirac-point in the topologically protected surface state (TSS) of topological insulators (TIs) by strong electric fields with frequencies in the THz range gives rise to a nontrivial type of unusually efficient high-harmonic generation (HHG) as demonstrated for Bi2Te3 [1]. The long scattering times in the TSS resulting from spin-momentum locking are imprinted in the observation that the high-harmonic orders can be continuously shifted in frequency by varying the carrier-envelope phase of the driving field. This makes it possible to investigate the unusual transport properties in the TSS by this all optical method even at buried interfaces.
Here, we present first results for Bi2Se3 by using a newly developed setup that enables THz-HHG with a stable carrier-envelope phase at a repetition rate of 200 kHz reaching field strengths of up to 10 MV/cm in the frequency range of 12-90 THz. We show how the contribution of electrons in the TSS to the HHG spectra can be determined by measurements with varying field strengths and THz-frequencies above and below the bulk band gap, while analyzing the polarization of the high harmonic signal for different directions of the excitation in momentum space.
[1] C. P. Schmid et al., Nature 593, 385 (2021).