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O: Fachverband Oberflächenphysik

O 23: Ultrafast Electron Dynamics at Surfaces and Interfaces III

O 23.3: Talk

Tuesday, March 19, 2024, 11:00–11:15, MA 041

Subcycle time-resolved THz-ARPES of Bi₂Te₃ in two-dimensional momentum space — •Tim Bergmeier, Suguru Ito, Jens Güdde, and Ulrich Höfer — Fachbereich Physik, Philipps-Universität Marburg

Angle-resolved photoemission spectroscopy (ARPES) combined with Terahertz (THz) excitation and subcycle temporal resolution offers unique capabilities for investigating the ultrafast electron dynamics of Dirac currents in the surface band of topological insulators [1]. At field strengths that are strong enough for high-harmonic generation [2], it has recently been shown in Bi₂Te₃ that this technique can even track the buildup and dephasing of Floquet-Bloch states along one particular direction parallel to the surface [3]. A full two-dimensional (2D) momentum mapping of optically excited Dirac currents, however, has been so far demonstrated only without subcycle time resolution [4].

Here, we present first results on subcycle-resolved THz-ARPES on Bi₂Te₃ in the full 2D momentum space of the surface with a recently developed experimental setup. It combines the generation of few-cycle THz-pulses in the frequency range of 12-90 THz, which allow for field strengths of several MV/cm on the sample surface, with an ultrashort 400-nm two-photon probe of less than 15 fs duration at a repetition rate of 200 kHz.
[1] J. Reimann et al., Nature 562, 396 (2018).
[2] C. P. Schmid et al., Nature 493, 385 (2021).
[3] S. Ito et al., Nature 616, 696 (2023).
[4] J. Reimann et al., Sci. Rep. 13, 5796 (2023).

Keywords: ARPES; THz; Bi2Te3; Subcycle; Topological Insulator