Berlin 2018 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 6: Ultrafast magnetism I
MA 6.5: Vortrag
Montag, 12. März 2018, 10:30–10:45, EB 407
Ultrafast magnetization and lattice dynamics: non-thermal effects — •Karel Carva1, Pablo Maldonado2, Pavel Balaz1, and Peter M. Oppeneer2 — 1Charles University, DCMP, Ke Karlovu 5, CZ-12116, Prague, Czech Republic — 2Uppsala University, PO Box 516, 75120 Uppsala, Sweden
Femtosecond lasers allow to observe magnetization dynamics on an unprecedently short timescale. This dynamics is often described employing the three temperature model, without verifying its validity.
Here we study magnetization dynamics with a special emphasis to non-thermal effects. We have calculated electron-phonon scattering rates for systems with a high electronic temperature, and phonon lifetimes due to phonon-phonon scattering. From these we obtain phonon populations that differ sharply from the thermal ones within picoseconds after the pump [1]. This allows us to understand recent experimental observations and disproves the applicability of the model based on one lattice temperature here [2].
Another important consequence of ultrafast demagnetization is the presence of spin currents described by the superdiffusive spin transport model [3]. This is also a non-thermal effect since electrons with energy significantly above the Fermi level play crucial role there. We compare it to its thermal counterpart, the spin-dependent Seebeck effect.
[1] P. Maldonado et al., Phys. Rev. B 96, 174439 (2017)
[2] T. Henighan et al., Phys. Rev. B 93, 22030 (2016)
[3] M. Battiato et al., Phys. Rev. Lett. 105, 027203 (2010)