Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 39: Focussed session: Theory and computation of electronic structure: new frontiers III (jointly with HL, DS)
O 39.5: Vortrag
Mittwoch, 16. März 2011, 12:15–12:30, TRE Phy
Laser-induced ultrafast demagnetization: First-principles analysis of Elliott-Yafet processes — •Karel Carva1,2 and Peter M. Oppeneer2 — 1Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, CZ-12116 Prague 2, Czech Republic — 2Department of Physics and Materials Science, Uppsala University, Box 530, SE-75121 Uppsala, Sweden
The laser-induced ultrafast demagnetization phenomenon has attracted a lot of attention since the first successful experiment on the fs timescale in 1996. However even now it is still far from being understood on the microscopic level. A number of possible microscopic mechanisms have been proposed.
Here we concentrate on Elliott-Yafet spin relaxation due to to electron-phonon scattering in Ni. The spin-flip probability associated with electron-phonon scattering in Ni has been estimated - employing the ab initio band structure - to be larger than expected. We calculate the spin-flip Eliashberg function based on ab initio electron-phonon coupling matrix elements to obtain the spin-flip probability with much higher accuracy. We extend this method to the regime of non-equilibrium electron distributions relevant for ultrafast processes. We find significant differences between the efficiency of this spin relaxation mechanism for highly non-equilibrium electron distributions pumped by the laser and thermalized ones (not in equilibrium with lattice).