Dresden 2014 – scientific programme
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MA: Fachverband Magnetismus
MA 29: Magnetization Dynamics II
MA 29.6: Talk
Wednesday, April 2, 2014, 16:30–16:45, HSZ 401
Ab initio study of relativistic effects in femtosecond magneto-optics — Ritwik Mondal1, Karel Carva1,2, and •Peter M. Oppeneer1 — 1Uppsala University, Uppsala, Sweden — 2Charles University, Prague, Czech Republic
Excitation of a metallic ferromagnet such as Ni with an intensive femtosecond laser-pulse causes an ultrafast demagnetization within approximately 300 fs. It has been proposed that the ultrafast demagnetization, which is measured in femtosecond magneto-optical experiments, could be due to relativistic light-induced processes: either direct light-induced spin-flip processes or coherent relativistic quantum electrodynamics [1,2] (see also [3]). We perform an ab initio investigation of the influence of these relativistic effects on the magneto-optical response of Ni. To this end, we compute, first, the influence of relativistic spin-flip transitions, and second, develop a response theory formulation of the additional appearing ultra-relativistic terms in the Foldy-Wouthuysen transformed Dirac Hamiltonian due to the electromagnetic field. This allows us to draw conclusions on the amount of demagnetization that could be achieved by these mechanisms. Financial support from the EU (under grant No. 281043, FemtoSpin) is acknowledged. [1] J.-Y. Bigot, M. Vomir, E. Beaurepaire, Nature Phys. 5, 515 (2009). [2] G.P. Zhang, W. Hübner, G. Lefkidis, Y. Bai, T.F. George, Nature Phys. 5, 499 (2009). [3] K. Carva, M. Battiatio, P.M. Oppeneer, Nature Phys. 7, 665 (2011).