Quasiequilibrium gas of magnons with a nonzero chemical potential: A way to Bose-Einstein condensation

Abstract

A gas of thermalized quasiequilibrium magnons with a nonzero chemical potential is created in an yttrium iron garnet film using parametric pumping. The value of the chemical potential is determined directly by detection of the statistic distribution of magnons over the spectrum. With increasing pumping power, the value of the chemical potential increases. At high pumping powers, it can reach the energy corresponding to the lowest magnon frequency. Under these conditions, a very narrow peak of magnon population at the lowest magnon frequency is created. We associate this peak with Bose-Einstein condensation of magnons.