Regensburg 2022 – scientific programme
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O: Fachverband Oberflächenphysik
O 16: Poster Monday: Ultrafast Processes 1
O 16.11: Poster
Monday, September 5, 2022, 18:00–20:00, P4
Ultrafast Transport and Energy Relaxation of Hot Electrons in Au/Fe/MgO(001) Investigated by Linear Time-resolved Photoelectron Spectroscopy — •Florian Kühne1, Yasin Beyazit1, Detlef Diesing2, Ping Zhou1, Jesumony Jayabalan1, and Uwe Bovensiepen1 — 1University of Duisburg-Essen,Physics — 2University of Duisburg-Essen, Chemistry
Optically excited electrons and holes are of particular interest in solid-state physics because analysis of their dynamics allows a microscopic understanding of the interactions in non-equilibrium states. Here we want to discern the relaxation by such local inelastic processes and non-local transport effects. To analyze the ultrafast dynamics of charge carriers in the vicinity of the Fermi energy EF, femtosecond time-resolved linear photoelectron spectroscopy was applied. We report on first experimental results obtained by using 1.55 eV pump and 6 eV probe photons on an Au/Fe/MgO(001) epitaxial heterosystem, complementary to previous work in Beyazit et al., PRL 125, 076803 (2020). By pumping the Fe side, hot electrons are excited in the Fe layer, and subsequently injected into the Au layer and propagate to the surface, where they are probed by photoelectron emission spectroscopy. In the Fe side pumped data, we observe thickness dependent differences in relaxation compared to the Au side pumped data. In Au side pumping we observe efficient transport into the Fe layer. We will present an energy E dependent analysis of the propagation and energy density U(E,dAu) of electrons above EF, which together with a two-temperature model shows a super diffusive transport limit.