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MA: Fachverband Magnetismus
MA 43: Magnetization Dynamics II of 3
MA 43.11: Talk
Thursday, March 14, 2013, 17:30–17:45, H22
Phonon mediated Bose-Einstein magnon condensation — •Peter Clausen1, Dmytro A. Bozhko1,2, Andrii V. Chumak1, Alexander A. Serga1, Gennadii A. Melkov2, and Burkard Hillebrands1 — 1Fachbereich Physik and Landesforschungszentrum OPTIMAS, TU Kaiserslautern, Germany — 2Faculty of Radiophysics, Taras Shevchenko National University of Kyiv, Ukraine
We report on the first observation of a magneto-elastic magnon (MEM) mode populated due to the thermalization of a parametrically driven magnon gas. The gas behavior is investigated by time- and wavevector-resolved Brillouin light scattering (BLS) spectroscopy in an yttrium iron garnet (YIG) film. Two peaks of the magnon density with very similar energies but different wavevectors are observed near the bottom of the magnon spectrum. The magnons with the lower wavevector are identified as a Bose-Einstein magnon condensate (BEC) and the others with an approximately two-times larger wavevector as the MEM mode.
Our investigations show that the MEM mode starts to be visible at pumping powers at least ten times smaller than the threshold of the BEC formation. Furthermore, in contrast to the BEC peak, the width of the MEM mode peak is practically independent from the magnon density. The population characteristic of the MEM mode can be understood as a result of a phonon induced coupling of high magnon modes, and thus the formation of an effective transfer channel of the thermalized magnons to the bottom of the spin-wave spectrum.
Support by the DFG within the SFB/TRR 49 is gratefully acknowledged.