SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 67: Poster Session V: Ultrafast electron dynamics at surface and interfaces I

O 67.3: Poster

Mittwoch, 3. März 2021, 10:30–12:30, P

Ultrafast Dynamics of Hot Electrons and Holes by Femtosecond Photoelectron Spectroscopy in Au/Fe/MgO(001) — •Florian Kühne¹, Yasin Beyazit¹, Detlef Diesing², Ping Zhou¹, and Uwe Bovensiepen¹ — ¹University of Duisburg-Essen, Physics, Germany — ²University of Duisburg-Essen, Chemistry

Optically excited electrons and holes are of particular interest in solid state physics, because they allow a microscopic understanding of interactions in non-equilibrium states. Here we aim at discerning electronic relaxation by local inelastic processes and non-local transport. To analyze the ultrafast dynamics of charge carriers in the vicinity of the Fermi energy E_F, femtosecond time-resolved linear photoelectron spectroscopy was applied and we report on results obtained by using 1.55 eV pump and 6 eV probe photons on Au/Fe/MgO(001), complementary to previous work in Beyazit et al., PRL 125, 076803 (2020). In case of the back side pumping, hot electrons are excited in the Fe, are injected into Au and propagate to the surface, where they are probed by photoelectron emission spectroscopy. We observe a positive shift in the time delay of the transient intensity increasing with d_Au in comparison to the front pump data, which is attributed to transport effects in Au. The analyzed electron distribution in the vicinity of E_F indicates a symmetric excitation of electrons and holes. It can be described by a Fermi-Dirac distribution function. We estimate a maximum increase in the electron temperature by 50 K, which builds up within 100fs and then decays by energy transfer to phonons.

This work was funded by the DFG through the CRC 1242.