Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 72: Poster: Scanning Probe Microscopy: Light Matter Interaction at Atomic Scales

O 72.4: Poster

Wednesday, March 20, 2024, 18:00–20:00, Poster D

Time-Resolved Measurements with THz-STM on Semiconducting MoTe₂ — •Vibhuti Rai, Junyoung Sim, Carlos Williams, 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

To access time scales of elementary excitations, pump-probe schemes using ultrashort laser pulses are the method of choice. Combining these with scanning tunnelling microscopy (STM) would not only give the required time resolution but also provide spatial resolution on the sub nanometer scale [1]. In this work, we use a home-built THz setup combined with an STM working at 5K in ultra-high vacuum. We study the charge carrier dynamics of the semiconducting MoTe₂ bulk sample [2]. An infrared pump pulse is used to excite the sample across its direct band gap of 1eV. To probe the dynamics, we use the THz field as a transient bias that modulates the tunnelling junction. By delaying the IR pulse with respect to the THz pulse, we explore the dynamics of the excited states and also use them further to spatially resolve and study surface defects.

Keywords: THz spectroscopy; Light-matter interaction; Scanning tunnelling microscopy (STM); Charge carrier dynamics; Pump-probe scheme