Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 52: Poster Session - New Methods: Experiments

O 52.2: Poster

Tuesday, March 17, 2020, 18:15–20:00, P2/1OG

Design of an ultrafast THz-STM — •Nils Bogdanoff, Sergey Trishin, Christian Lotze, Katharina J. Franke, and Tobias Kampfrath — Freie Universität Berlin, Department of Physics, Arnimallee 14, 14195 Berlin, Germany

Investigating the ultrafast dynamics of electronically excited systems is crucial for understanding its coupling to the environment. Most state-of-the-art ultrafast techniques are used to investigate isolated systems in gas-phase or applied to macroscopic surface areas of carefully tailored systems. However, many modern applications strive towards increasingly small, surface-coupled structures approaching the atomic scale. A standard technique for high electronic real-space resolution is scanning tunneling microscopy (STM). Its temporal resolution is limited by the bandwith of the amplifier, cabling and the junction capacity itself. In 2013 Cocker et al. demonstrated that applying a pulse of THz radiation to the junction of an STM can act as a transient bias voltage opening a tunneling channel only for an ultrashort period of time [1]. Using this in a pump-probe scheme and recording changes in the average tunneling current makes ultrashort timescales accessible by STM [1,2]. Here we present first steps on the way to constructing and characterizing a THz-STM using a tilted-pulse-front pumping scheme to generate THz-pulses in a lithium niobate (LN) crystal.

[1] Cocker, T. et al. An ultrafast terahertz scanning tunnelling microscope. Nature Photon 7, 620-625 (2013)

[2] Cocker, T. et al. Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging. Nature 539, 263-267 (2016)