Regensburg 2016 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 48: Poster Session II
MA 48.9: Poster
Donnerstag, 10. März 2016, 15:00–18:00, Poster B1
Magnon supercurrent in a magnon Bose-Einstein condensate subject to a thermal gradient — •Dmytro A. Bozhko1,2, Peter Clausen1, Vitaliy I. Vasyuchka1, Gennadii A. Melkov3, Burkard Hillebrands1, Victor S. L’vov4, and Alexander A. Serga1 — 1Fachbereich Physik and Landesforschungszentrum OPTIMAS, TU Kaiserslautern, Germany — 2Graduate School Materials Science in Mainz, Germany — 3Taras Shevchenko National University of Kyiv, Ukraine — 4Weizmann Institute of Science, Israel
Bose-Einstein magnon condensation (BEC), the spontaneous appearance of a coherent state at the global energy minima of the spin-wave spectrum possesses zero group velocity. The presented here dynamics of a magnon BEC in a thermal gradient provides the first evidence of the formation of a magnon supercurrent at room temperature. The magnon dynamics was revealed by time- and wavevector-resolved Brillouin light scattering spectroscopy. It has been found that the freely evolving magnon BEC in a parametrically pumped spin system of a single-crystal film of yttrium iron garnet decays faster with the increase of a probing laser beam power. The behavior of the rest of the magnon gas remains undisturbed. A uniform sample heating does not affect the BEC behavior. Thus, the observed effect can be treated as the outflow of condensed magnons from the laser focal point due to the phase difference induced in the BEC wave function by a temperature gradient. The developed theoretical model perfectly describes the experimental data. The work is supported by the DFG within the SFB/TR 49.