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O: Fachverband Oberflächenphysik
O 13: Ultrafast Electron Dynamics at Surfaces and Interfaces II
O 13.3: Talk
Monday, March 18, 2024, 15:45–16:00, MA 041
Spatio-Temporal Electron Propagation Dynamics in Au/Fe/MgO(001) in Nonequilibrium Analyzed by Femtosecond Two-Photon Photoemission — •Florian Kühne1, Markus Heckschen1, Yasin Beyazit1, Elaheh Shomali1, Jesumony Jayabalan1, Ping Zhou1, Detlef Diesing2, Markus Gruner1, Rossitza Pentcheva1, Axel Lorke1, Björn Sothmann1, and Uwe Bovensiepen1 — 1Fakultät für Physik, Universität Duisburg-Essen and CENIDE, Duisburg D-47048, Germany — 2Fakultät für Chemie, Universität Duisburg-Essen and CENIDE
Optically excited electrons in metals travel ballistically on a femtosecond timescale until they scatter due to electron-electron or electron-phonon interactions. To gain a deeper understanding of the ballistic and few times scattered electrons under non-equilibrium conditions we combine time-resolved two-photon photoelectron emission spectroscopy with real-time time-dependent density functional theory(RT-TDDFT) as well as a random-walk-like transport simulation, see Heckschen et al., PRX Energy 2, 043009(2023). Here, we discuss the experimental details using a back-side pumped geometry on a MgO/Fe/Au epitaxial heterostructure probing the Au surface. The time-delayed response of the photoelectrons at lower energies is used to investigate transport and scattering pathways. Analyzing this time delay of 10 to 100fs shows an apparent acceleration with increasing film thickness. We find the electron trajectories angular dependence is of key importance to explain this effect. Funding by the DFG through Project No. 278162697 - SFB1242 is gratefully acknowledged.
Keywords: Photoemission; Transport; Random walk simulation; back-side pump; time-resolved