Kinetics of Bose-Einstein condensation of magnons in Yttrium Iron Garnet films

TL;DR

This paper develops a kinetic theory to explain the dynamics of magnon Bose-Einstein condensation in Yttrium Iron Garnet films, resolving discrepancies between experiments and earlier models by considering relaxation times and effective temperature effects.

Contribution

It introduces a Boltzmann kinetic equation approach to describe magnon condensation, clarifying the role of relaxation times and effective temperature in the process.

Findings

Relaxation time exceeds experimental duration, affecting condensate behavior.

Kinetic theory relates critical pumping power to effective magnon temperature.

Resolved contradictions between experimental results and previous theoretical predictions.

Abstract

In this article, we explain the reason of the apparent contradiction between recent experiments [1] and [2] and earlier theoretical predictions [3] of strongly asymmetric condensate resulting in attractive interaction between the condensate magnons. We show that the relaxation time for equilibrium between two condensates at two minima of energy exceeds the time of experiment. Therefore, it should be described by Boltzmann kinetic equation. We develop the proper kinetic theory and find the relation between the critical pumping power and the effective temperature of over-condensate magnons.