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MA: Fachverband Magnetismus

MA 42: Posters Magnetism I

MA 42.30: Poster

Mittwoch, 18. März 2020, 15:00–18:00, P3

Relaxation of classical spins coupled to a conduction-electron system with dissipative boundaries — •Michael Elbracht and Michael Potthoff — I. Institute of Theoretical Physics, Department of Physics, Universität Hamburg

The real-time dynamics of a few classical impurity spins locally exchange-coupled to a conduction-electron system is investigated numerically. Starting from a locally excited initial state with a noncollinear impurity-spin configuration, we study the energy and spin dissipation as well as the final relaxation to the ground state. To circumvent finite size effects, a dissipative Lindblad bath is coupled to the system edges which absorbs the outgoing spin excitations. This allows a study of unperturbed real-time dynamics on essentially arbitrary long time scales.

The long-time relaxation of the classical impurity spins is traced as a function of various parameters, such as the exchange interaction or the number and the position of the spins. While the system in fact relaxes completely for an even number of impurity spins, an incomplete relaxation is observed for an odd number, i.e., the system stays in a metastable state. This unconventional behavior is attributed to additional symmetries that dynamically emerge and constrain the time evolution for states with an average energy already close to the ground state energy. The odd-even effect is understood by linearizing the equations of motion close to the manifold of classically degenerate ground states.