Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 29: Focus Session: Magnon Polarons – Magnon-Phonon Coupling and Spin Transport (joint session MA/HL)

MA 29.3: Invited Talk

Wednesday, March 18, 2020, 10:30–11:00, HSZ 04

Anisotropic transport of spontaneously accumulated magneto-elastic bosons in yttrium iron garnet films — •Alexander A. Serga — Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaisersalutern, Germany

It is well known that bosonic quasiparticles as excitons, polaritons or magnons are able to spontaneously form Bose-Einstein condensates (BECs). However, interactions between quasiparticles of a different nature, for example, between magnons and phonons, can significantly alter their properties and, thus, modify the condensation scenarios.

Here, I present a novel condensation phenomenon mediated by the magnon-phonon interaction: a bottleneck accumulation of hybrid magneto-elastic bosons—magnon polarons. Similar to the magnon BEC, the phenomenon is observed in a microwave-driven single-crystal ferrimagnetic film. However, unlike BEC, which is a consequence of equilibrium Bose statistics, the bottleneck accumulation is determined by varying interparticle interactions. Furthermore, the accumulated quasiparticles possess a nonzero group velocity. Our recent 2D transport measurements show the simultaneous formation of a few distinct magnon-polaron groups, which propagate in film plane as spatially localized beams with different group velocities. The role of the magneto-elastic anisotropy in the beam formation and interaction of the accumulated quasiparticles with the magnon BEC are discussed.

Financial support of this work by the European Research Council Advanced Grant “SuperMagnonics” is gratefully acknowledged.