Bottleneck accumulation of hybrid bosons in a ferrimagnet
Dmytro Bozhko (TU Kaiserslautern)

An ensemble of spin wave quanta, also known as magnons, can be treated as a Bose gas of weakly interacting quasi-particles. The excessive excitation of magnons in the system causes an increase in the chemical potential of a thermalized magnon gas. When it becomes equal to the minimal magnon energy a magnon Bose-Einstein condensate (BEC) may form at this spectral point. However, magnon-phonon interaction processes can significantly modify condensation scenario. Our observations of the magnon BEC in a single-crystal film of yttrium iron garnet (Y3Fe5O12) by means of wavevector-resolved BLS spectroscopy resulted in the discovery of a novel condensation phenomenon mediated by magneto-elastic interaction: A spontaneous accumulation of hybrid magnon-phonon bosonic quasi-particles at the intersection of the lowest spin-wave mode and a transversal acoustic wave.