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MA: Fachverband Magnetismus
MA 2: Ultrafast Magnetization I
MA 2.1: Vortrag
Montag, 16. März 2020, 09:30–09:45, HSZ 101
Theory of out-of-equilibrium electron and phonon dynamics after laser excitation in metals — •Ulrike Ritzmann1,2,3, Peter M. Oppeneer1,3, and Pablo Maldonado3 — 1Fachbereich Physik, Freie Universität Berlin, Berlin, Germany — 2Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, Berlin, Germany — 3Department of Physics and Astronomy, Uppsala University, Uppsala, Germany
Ultrafast magnetization phenomena are often described using the two- temperature model (2TM) to compute the electron and phonon dynamics after laser excitation. This model assumes that both subsystems are locally at thermal equilibrium. However, recent experiments show that this description is not sufficient to describe the out-of-equilibrium dynamics on ultrashort timescales. Here, we present a parameter-free microscopic out-of-equilibrium model to describe the ultrafast laser- induced system dynamics in various nonmagnetic and magnetic metals such as gold, aluminium, iron, nickel and cobalt. We report strong deviations from the 2TM on the picosecond timescale for all materials studied. Furthermore, we demonstrate the importance of the mode-dependence of the electron-phonon coupling for the relaxation process and reveal the significance of this channel in the lattice equilibration. The computed new behavior demonstrates that phonon-mode dependent dynamics have to be considered in the ps time range in order to describe properly the lattice heating process and the subsequent dynamics of the whole system.