Bozhko Dmytro A, Clausen Peter, Melkov Gennadii A, L'vov Victor S, Pomyalov Anna, Vasyuchka Vitaliy I, Chumak Andrii V, Hillebrands Burkard, Serga Alexander A
Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
Graduate School Materials Science in Mainz, Kaiserslautern 67663, Germany.
Phys Rev Lett. 2017 Jun 9;118(23):237201. doi: 10.1103/PhysRevLett.118.237201. Epub 2017 Jun 8.
An ensemble of magnons, quanta of spin waves, can be prepared as a Bose gas of weakly interacting quasiparticles. Furthermore, the thermalization of the overpopulated magnon gas through magnon-magnon scattering processes, which conserve the number of particles, can lead to the formation of a Bose-Einstein condensate at the bottom of a spin-wave spectrum. However, magnon-phonon scattering can significantly modify this scenario and new quasiparticles are formed-magnetoelastic bosons. Our observations of a parametrically populated magnon gas in a single-crystal film of yttrium iron garnet by means of wave-vector-resolved Brillouin light scattering spectroscopy evidence a novel condensation phenomenon: A spontaneous accumulation of hybrid magnetoelastic bosonic quasiparticles at the intersection of the lowest magnon mode and a transversal acoustic wave.
磁振子（自旋波的量子）系综可被制备成弱相互作用准粒子的玻色气体。此外，通过守恒粒子数的磁振子 - 磁振子散射过程，过填充磁振子气体的热化可导致在自旋波谱底部形成玻色 - 爱因斯坦凝聚。然而，磁振子 - 声子散射会显著改变这种情况，并形成新的准粒子——磁弹玻色子。我们通过波矢分辨布里渊光散射光谱对钇铁石榴石单晶薄膜中参量填充磁振子气体的观测证明了一种新颖的凝聚现象：在最低磁振子模式与横向声波的交点处，混合磁弹玻色子准粒子的自发积累。
