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arXiv · 1803.11548

From Kinetic Instability to Bose-Einstein Condensation and Magnon Supercurrents

Alexander J. E. Kreil·Dmytro A. Bozhko·Halyna Yu. Musiienko-Shmarova·Victor S. L'vov·Anna Pomyalov·Burkard Hillebrands·Alexander A. Serga
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Abstract

Evolution of an overpopulated gas of magnons to a Bose-Einstein condensate and excitation of a magnon supercurrent, propelled by a phase gradient in the condensate wave function, can be observed at room-temperature by means of the Brillouin light scattering spectroscopy in an yttrium iron garnet material. We study these phenomena in a wide range of external magnetic fields in order to understand their properties when externally pumped magnons are transferred towards the condensed state via two distinct channels: A multistage Kolmogorov-Zakharov cascade of the weak-wave turbulence or a one-step kinetic-instability process. Our main result is that opening the kinetic instability channel leads to the formation of a much denser magnon condensate and to a stronger magnon supercurrent compared to the cascade mechanism alone.

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Alexander J. E. Kreil, Dmytro A. Bozhko, Halyna Yu. Musiienko-Shmarova, Victor S. L'vov, Anna Pomyalov, Burkard Hillebrands, Alexander A. Serga. 2018-03-30. From Kinetic Instability to Bose-Einstein Condensation and Magnon Supercurrents. https://doi.org/10.1103/physrevlett.121.077203

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