Mechanism for a chemical potential of nonequilibrium magnons in parametric parallel pumping

I present a new theory of parametric parallel pumping for a ferrimagnet and demonstrate a mechanism by which a chemical potential of nonequilibrium magnons is generated [1]. In the parametric parallel pumping, two magnetic fields parallel to each other are used; one is static, and the other is time-periodic. By using this pumping, we can achieve a nonequilibrium state in which the magnon distribution function is approximated by the Bose distribution function with a finite chemical potential. However, its mechanism has been unclear. In this talk, I will discuss how nonequilibrium magnons in the parametric parallel pumping acquire a finite chemical potential [1].

[1] N. Arakawa, J. Phys. Soc. Jpn. 88, 084704 (2019).