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HL: Fachverband Halbleiterphysik

HL 6: Focus Session: Magnon Polarons - Magnon-Phonon Coupling and Spin Transport (joint session MA/HL)

HL 6.3: Hauptvortrag

Montag, 27. September 2021, 14:30–15:00, H5

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

Interaction between quasiparticles of a different nature, such as magnons and phonons, leads to mixing their properties and forming hybrid states in the areas of intersection of individual spectral branches. In garnet ferrite films, such hybridization results in a resonant increase in the efficiency of the spin Seebeck effect and the spontaneous bottleneck accumulation of hybrid magnetoelastic bosons—magnon polarons.

Similar to the Bose-Einstein magnon condensation (BEC), the latter phenomenon occurs in a yttrium iron garnet film exposed to microwaves. However, unlike the BEC, which is a consequence of the equilibrium Bose statistics, the bottleneck accumulation is determined by changing interparticle interactions. Studying the transport properties of accumulated quasiparticles, we found that such accumulation occurs in two frequency-distant groups: quasiphonons and quasimagnons. These quasiparticles propagate in the film plane as spatially localized beams with different group velocities. The developed theoretical model qualitatively describes the double accumulation effect, and the analysis of the two-dimensional quasiparticle spectrum makes it possible to determine the wavevectors and frequencies of each group.

Funded by the ERC Advanced Grant 694709 SuperMagnonics and by the DFG within TRR 173 – 268565370 (project B04).