Optical cooling of magnons

TL;DR

This paper models how inelastic light scattering in magneto-optical resonators can cool magnons in magnetic insulators like YIG, potentially reducing magnetic temperature significantly with current technology.

Contribution

It introduces a theoretical model for optical magnon cooling in magnetic insulators, highlighting the role of light intensity in controlling magnon temperature.

Findings

Magnons can be cooled via inelastic light scattering.

Magnon temperature is controllable by light intensity.

Cooling can significantly reduce magnetic order temperature.

Abstract

Inelastic scattering of light by spin waves generates an energy flow between the light and magnetization fields, a process that can be enhanced and controlled by concentrating the light in magneto-optical resonators. Here, we model the cooling of a sphere made of a magnetic insulator, such as yttrium iron garnet (YIG), using a monochromatic laser source. When the magnon lifetimes are much larger than the optical ones, we can treat the latter as a Markovian bath for magnons. The steady-state magnons are canonically distributed with a temperature that is controlled by the light intensity. We predict that such a cooling process can significantly reduce the temperature of the magnetic order within current technology.