Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

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

O 72.5: Poster

Mittwoch, 20. März 2024, 18:00–20:00, Poster D

Coupling Single-Cycle Terahertz Fields into a STM: Characterization and Time-Resolved Measurements — •Junyoung Sim, Vibhuti Rai, Carlos Williams, Sergey Trishin, Nils Bogdanoff, Tom Seifert, Tobias Kampfrath, Christian Lotze, and Katharina Franke — Freie Universtiät Berlin, Department of Physics, Arnimallee 14, 14195 Berlin, Germany

Scanning tunneling microscopy (STM) is an ideal tool to study the structure and electronic properties of atomic-scale nanostructures on surfaces. Excitation-relaxation dynamics in these systems occur typically on timescales of picoseconds or even faster, which is beyond the electronic bandwidth of STM. To explore this ultrafast regime, Cocker et al. coupled ultrashort terahertz (THz) pulses into a STM junction and implemented a pump-probe detection scheme [1].

In this work, we follow a similar approach by setting up a THz source and coupling it to a 5K- STM. Here, we provide a preliminary characterization of our set up with a few benchmarking experiments. We measure the near-field THz pulse that modulates the photocurrent excited by a preceding optical pulse between STM tip and Ag(111) surface. We also probe field emission resonance by the transient voltage from the THz pulse. We then perform infrared-pump THz-probe measurement to investigate the dynamics of excitation processes across the bandgap on the semiconducting transition metal dichalcogenide MoTe2 [2].

[1] Cocker et al. Nature Photonics 15, 558-569 (2021)

[2] Sankar et al. Chem. Mater., 29, 2, 699-707 (2017)

Keywords: Scanning Tunneling Microscpy; Terahertz