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O: Fachverband Oberflächenphysik
O 79: Poster Session VI: Ultrafast electron dynamics at surface and interfaces II
O 79.4: Poster
Wednesday, March 3, 2021, 13:30–15:30, P
Optical driven 4f-spin and orbital transitions in rare-earth metals — •N. Thielemann-Kühn1, T. Amrhein1, W. Bronsch1, S. Jana2, N. Pontius2, R. Y. Engel3, P. S. Miedema3, M. Beye3, B. E. van Kuiken4, M. Teichmann4, R. E. Carley4, L. Mercadier4, A. Yaroslavtsev4, G. Mercurio4, L. Le Guyader4, N. Agarwal4, A. Scherz4, P. M. Oppeneer5, M. G. Weinelt1, and C. Schüßler-Langeheine2 — 1FU Berlin — 2HZB — 3DESY — 4EuXFEL — 5Uppsala University
4f rare earth (RE) metals exhibit strongly localized 4f states carrying the largest magnetic moment among the elements of the periodic table. Due to their energy-level scheme, 4f states are not directly accessible with optical wavelengths in contrast to the delocalized 5d6s valence electrons, that mediate the inter-atomic 4f exchange coupling. Despite the strong intra-atomic exchange coupling, local 5d-4f excitations have neither been observed upon optical excitation nor were considered to be relevant for non-equilibrium dynamics in RE metal based systems. In an X-ray absorption experiment at the EuXFEL we found that the 5d and 4f system interact directly via inelastic electron scattering and 4f-5d electron transfer, initiating transitions to higher energetic 4f configurations, which becomes pronouncedly visible in a change of the multiplet structure. The observed 4f electronic excitation are highly element-specific and strongly depend on pump pulse parameter. They directly cause changes in exchange and electron-phonon coupling and thus open a door for more fundamental understanding of non-equilibrium dynamics.