Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 8: Ultrafast Electron Dynamics I: Surfaces and Interfaces (joint session O/MA)
O 8.8: Talk
Monday, March 16, 2020, 12:15–12:30, TRE Phy
Local and non-local electron dynamics of Au/Fe/MgO(001) heterostructures analyzed by time-resolved two-photon photoemission spectroscopy — Yasin Beyazit1, Jan Beckord1, Ping Zhou1, Jan Philipp Meyburg2, Detlef Diesing2, Manuel Ligges1, and •Uwe Bovensiepen1 — 1University of Duisburg-Essen, Faculty of Physics and Center for Nanointegration (CENIDE), 47048 Duisburg) — 2University of Duisburg Essen, Faculty of Chemistry, Universitätsstr. 5, 45711 Essen
The ultrafast electron dynamics at interfaces is determined by the competition of local scattering processes and transport effects. Employing femtosecond laser pulses in front and back side pumping of Au/Fe/MgO(001) [1] combined with detection in two-photon photoelectron emission spectroscopy we analyze local relaxation dynamics of excited electrons in buried Fe, injection into Au across the Fe-Au interface, and electron transport across the Au layer at 0.6 to 2.0 eV above the Fermi energy. By analysis as a function of Au film thickness we obtain the electron lifetimes of bulk Au and Fe and distinguish the relaxation in the heterostructure's constituents. We conclude further that electron injection across the epitaxial interface proceeds by electron wavepacket propagation. We also show that the excited electrons propagate through Au in a superdiffusive regime determined by few e-e scattering events. Application of such back side pumping photoelectron spectroscopy to further material systems will be discussed. Funding by the DFG through CRC 1242 is gratefully acknowledged. [1] Alekhin et al., J. Phys. Condens. Matter 31, 124002 (2019)