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O: Fachverband Oberflächenphysik

O 58: Poster Session - Ultrafast Electron Dynamics at Surface and Interfaces

O 58.5: Poster

Dienstag, 17. März 2020, 18:15–20:00, P2/2OG

Determining the orientation of transition dipoles of direct and indirect optical transitions in metals — •Tobias Eul, Michael Hartelt, Eva Prinz, Benjamin Frisch, Martin Aeschlimann, and Benjamin Stadtmüller — Department of Physics and Research Center Optimas, University of Kaiserslautern

Understanding the hot electron dynamics and their energy and momentum dissipation mechanisms paves the way to enhance the performance of next-generation electronic and spintronic devices. This understanding can be obtained by the combination of time-resolved photoemission spectroscopy and the recently developed momentum microscopy. However, to properly determine the electron dynamics with these techniques, it is crucial to clearly identify the orbital character of the initial, intermediate and final states that lead to the emission of a photoelectron.

Here, we propose a theoretical framework to predict the nature of the involved electronic states from the cross-correlation signal of a monochromatic 2PPE experiment. Our theory is based on the density matrix formalism, showing a dependence of the ratio between minimum and maximum of the cross-correlation trace and the orientation of the transition dipole with respect to the polarization of the incident light. Our calculations are then compared to momentum microscopy results for direct and indirect optical transitions in Ag(110), using both a phase-averaged and a phase-resolved pump-probe setup with a photon energy of 3.1eV. The comparison shows that the transition dipoles for direct transitions align along the ΓL-direction of the crystal.