Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 54: Scanning Probe Microscopy: Light Matter Interaction at Atomic Scales I
O 54.3: Vortrag
Mittwoch, 20. März 2024, 15:45–16:00, MA 041
Time-domain Detection of Ultrafast Voltage Transients in an STM Tunnel Junction — Vedran Jelic1, Stefanie Adams1, Mohamed Hassan1, Kaedon Cleland-Host1, •Spencer E. Ammerman2, and Tyler L. Cocker1 — 1Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA — 2EMPA, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
Lightwave-driven terahertz scanning tunneling microscopy (THz-STM) has emerged as a powerful tool for investigating ultrafast dynamics at atomic length scales. Illuminating the tunnel junction of an STM with a phase-stable single-cycle THz pulse has been shown to induce sub-picosecond tunneling currents coherently driven by the electric field of the THz transient, providing access to the local density of electronic states. A critical factor for interpretation of THz-STM measurements is knowledge of the ultrashort voltage transient. However, the THz transient is subject to spectral modification by variation in the nanoscale dielectric function, as shown by scanning near-field optical microscopy experiments. In order to distinguish between local samples properties and effects arising from terahertz-pulse coupling, a method for extracting the near-field transient is needed. Here, we demonstrate a THz-STM cross-correlation experiment for local time-domain sampling of the THz voltage transient. Combining self-consistent modeling and waveform shaping we introduce a generally applicable scheme for atomic-scale terahertz time-domain spectroscopy, spatially confined to an STM tunnel junction.
Keywords: Terahertz; Ultrafast Scanning Tunneling Microscopy; THz-STM; Simulation; Model