Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 97: Ultrafast Electron Dynamics at Surfaces and Interfaces III

O 97.8: Vortrag

Freitag, 5. April 2019, 12:15–12:30, H16

Microscopic energy flow dynamics in Fe/MgO — •Nico Rothenbach1, Markus E. Gruner1, Katharina Ollefs1, Ping Zhou1, Carolin Schmitz-Antoniak2, Niko Pontius3, Rolf Mitzner3, Christian Schüßler-Langeheine3, Rossitza Pentcheva1, Klaus Sokolowski-Tinten1, Renkai Li4, Mianzhen Mo4, Suji Park4, Xiaozhen Shen4, Stephen Weathersby4, Jie Yang4, Xijie Wang4, Heiko Wende1, Uwe Bovensiepen1, and Andrea Eschenlohr11University Duisburg-Essen and CENIDE — 2FZ Jülich — 3Helmholtz-Zentrum Berlin — 4SLAC

A localized optical excitation of a metal/insulator heterostructure, like a Fe/MgO multilayer, by a femtosecond (fs) laser pulse induces ultrafast dynamics like charge and spin transfer processes as well as coupling to low energy excitations mediated by e.g. electron-electron and electron-phonon scattering. We measure fs time- and element-resolved soft x-ray spectroscopy to separate and identify the electronic and lattice excitations. The latter is also analyzed by complementary ultrafast electron diffraction experiments. The response at the Fe L3-edge is maximal at 200 fs and represents local electronic excitations, coupling to phonons in Fe, and their relaxation to the insulator. The dynamics at the O K-edge reaches a maximal change after 400 fs, explained by lattice excitations of MgO due to energy transfer from Fe. Probing the O pre-edge gives rise to the interface states dynamics and deepens our understanding further. DFT calculations of layer-resolved vibrational and electronic DOS consolidate our interpretation. We acknowledge financial support by the DFG through the SFB1242.

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