Regensburg 2019 – scientific programme
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MA: Fachverband Magnetismus
MA 8: Magnonics
MA 8.5: Talk
Monday, April 1, 2019, 16:00–16:15, H52
Second sound in magnon Bose-Einstein condensate — •Halyna Yu. Musiienko-Shmarova1, Dmytro A. Bozhko1, Alexander J.E. Kreil1, Alexander A. Serga1, Anna Pomyalov2, Victor S. L’vov2, and Burkard Hillebrands1 — 1Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany — 2Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel
A macroscopic collective motion of a quantum condensate is commonly associated with phenomena such as superconductivity and superfluidity, often generalized by the term supercurrent. A quantum condensate supports also another type of motion – second sound. Second sound can be considered as a flow of elementary excitations of various types, which can propagate in a continuous medium with an almost linear dispersion law in the long-wavelength limit. Here, this refers to Bogoliubov waves with oscillations of both the amplitude and the phase of the Bose-Einstein Condensate’s (BEC) wave function. We discovered a Bogoliubov wave, magnon second sound, in a magnon BEC prepared by microwave parametric pumping in a room-temperature yttrium iron garnet film. Furthermore, we demonstrate a transition from the supercurrent-type to the second-sound-type motion of the magnon BEC. Financial support from the ERC Advanced Grant "SuperMagnonics" is acknowledged.