Spatio-Temporal Dynamics of Magnon Bose-Einstein Condensates

Recent advances in the studies of magnon gases have opened new horizons for the deep understanding of physics of room-temperature macroscopic coherent states including Bose-Einstein condensates of magnons. Although this phenomenon was discovered almost 15 years ago, a lot of important issues associated with the magnon Bose-Einstein condensation still remain unclear. Here I review the recent experimental achievements in the investigations of this phenomenon. I show that magnon condensates are characterized by high degree of temporal and spatial coherency, which enables, for instance, observation of the interference of two condensates in the real space.

I will also address the dynamics of the condensate in inhomogeneous time-varying external fields, resulting in discovery of the second sound in magnon condensates. Besides, these studies allowed us to answer the long-standing question concerning the physical origin of the spatial stability of the condensate.

Finally, I examine the applicability of the spin-current paradigm for description of magnon condensates.