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MA: Fachverband Magnetismus

MA 66: Poster 3

MA 66.22: Poster

Freitag, 24. März 2017, 09:30–13:00, P2-OG2

Inertia effects in the real-time dynamics of a quantum spin coupled to a Fermi sea — •Mohammad Sayad, Roman Rausch, and Michael Potthoff — I. Institut für Theoretische Physik, Universität Hamburg

Inertia effects in spin dynamics have been discussed intensively in the recent years by means of LLG-type approaches for classical spins only. However, in case of a quantum spin, inertia effects have not yet been studied. As compared to spin precession and damping, nutation is a higher-order effect, thus it is not a priori clear whether or not spin nutation is suppressed by quantum fluctuations. In order to clarify this issue, we consider the Kondo impurity model and study the spin dynamics, initiated by switching the direction of a magnetic field, by means of the time-dependent density-matrix renormalization group. We identify quantum effects by a systematic comparison of the spin dynamics for different spin quantum numbers S with the tight-binding spin-dynamics theory for the classical-spin Kondo model. We find a qualitative and with increasing spin-quantum numbers also quantitative agreement between quantum and semiclassical dynamics. The quantum-spin dynamics, however, exhibits a rapid damping of the nutational motion. Apart from the longitudinal spin dynamics reflecting the time-dependent Kondo effect, nutational damping is essentially the only characteristics of the quantum nature of the spin occurs on femtosecond-time scale and is basically independent of the relaxation time scale for the precessional motion.

M. Sayad et al., Europhys. Lett. 116, 17001 (2016)