Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 20: Poster Scanning Probe Microscopy: Light-Matter Interactions at the Atomic Scale

O 20.2: Poster

Montag, 17. März 2025, 18:00–20:00, P2

Local excitation of coherent phonons in 2H-MoTe₂ by THz driven scanning tunnelling microscope — Vibhuti Rai, Junyoung Sim, •Florian Faaber, Sergey Trishin, Nils Bogdanoff, Tom Seifert, Tobias Kampfrath, Christian Lotze, and Katharina J. Franke — Freie Universität Berlin, Department of Physics, Arnimallee 14,14195 Berlin, Germany

The coupling of THz pulses into a scanning tunnelling microscope has emerged as a unique technique to achieve picosecond time resolution while maintaining sub nanometer spatial resolution [1,2]. By delaying one THz pulse with respect to the other while recording the current rectified by the two pulses, a pump-probe scheme can be realized [3]. In this work, we use this scheme to investigate the quasi 2D semiconducting transition metal dichalcogenide (TMD) 2H-MoTe₂ at 7K in ultra-high vacuum and find a large oscillatory rectified current that is slowly decaying over 50 ps. We attribute these oscillations to the excitation of coherent phonons and discuss the effect of defects and DC bias voltage on the excited modes.

[1] Cocker, et al., Nature Photonics 7, 620*625 (2013)

[2] V. Jelic et al., Nature Physics 13, 591 (2017)

[3] T. L. Cocker et al., Nature 539, 263 (2016)

Keywords: Scanning tunnelling microscopy; Coherentphonon spectroscopy; THz excitations; Time-resolved measurements