Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 5: Ultrafast Electron Dynamics at Surfaces and Interfaces I

O 5.7: Vortrag

Montag, 18. März 2024, 12:00–12:15, MA 041

Ultrafast Low-Energy Photoelectron Diffraction for the Study of Adsorbate-Surface Interactions with 100 fs Temporal Resolution — •Hermann Erk, Carl Jensen, Stephan Jauernik, Petra Hein, and Michael Bauer — Christian-Albrechts-Universität Kiel, Germany

Ultrafast Low-Energy Electron Diffraction (ULEED) is a promising tool for studying the structural dynamics of ordered adsorbate layers following photoexcitation with femtosecond light pulses. However, the temporal spread of the probing electron pulse due to Coulomb interaction while it propagates toward the sample surface substantially limits the time resolution of this technique so far [1].

In this contribution, we present an alternative experimental scheme based on time- and angle-resolved ARPES that uses the photoelectrons generated in the substrate and diffracted by the adsorbate overlayer on the way to the electron detector to monitor ultrafast adsorbate structural dynamics. For tin-phthalocyanine adsorbed on single-crystalline graphite, we show that the intrinsic time resolution of the photoemission experiment of 100 fs is preserved in the diffraction process by the adsorbate overlayer. On a few ps timescale, we identify a transient and distinct decrease in the photoelectron diffraction intensity that we attribute to an increase in the adsorbate superlattice temperature due to phononic coupling with the substrate. The interpretation is substantiated by a comparison with phonon-temperature transients for graphite simulated based on a three-temperature model.

[1] S. Vogelgesang, et al. Nature Physics 14, 184 (2018)

Keywords: Phthalocyanine; Photoelectron Diffraction; ARPES; Graphite; Ultrafast