Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 43: Magnetization Dynamics III

MA 43.8: Vortrag

Donnerstag, 3. April 2014, 17:00–17:15, HSZ 401

Thermalization and Bose-Einstein condensation of magnons — •Julian Hüser and Tilmann Kuhn — Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

In 2006 Demokritov and co-workers observed clear evidence for room temperature Bose-Einstein condensation of magnons [1]. The BEC threshold was reached by increasing the magnon density by means of parametric pumping. The pumped magnons quickly redistributed over the spin wave spectrum and a macroscopic fraction finally accommodated the dispersion minimum leading to Bose-Einstein condensation.

Nevertheless, from the theoretical point of view the role of the different types of interaction processes among the magnons themselves and between magnons and phonons are still not well understood.

In this work we analyze the nonequilibrium dynamics of the hot magnon gas and the time evolution of the condensate by solving the quantum Boltzmann equation. We investigate the various types of interaction between magnons and phonons which can be grouped into two classes. The first type leads to a relaxation of the magnetic system whereas the second type keeps the magnon number constant thus only leading to an energy relaxation. We show that the latter interaction even enhances the condensate under certain conditions.

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[1] S. O. Demokritov, V. Demidov, O. Dzyapko, G. A. Melkov, A. A. Serga, B. Hillebrands, and A. N. Slavin, Nature 443, 430 (2006)