Bose condensation and spin superfluidity of magnons in a perpendicularly magnetized film of yttrium iron garnet

TL;DR

This paper experimentally investigates Bose-Einstein condensation and spin superfluidity of magnons in yttrium iron garnet films, revealing coherent magnon states with superfluid properties under radio-frequency pumping.

Contribution

It demonstrates the formation of magnon Bose condensates and spin superfluidity in yttrium iron garnet films, drawing parallels with superfluid helium-3 and exploring their stability mechanisms.

Findings

Magnon BEC forms a coherently precessing state.

Magnonic superfluidity exhibits stability due to repulsive magnon interactions.

Spatial distribution of condensate is affected by magnetic field gradients.

Abstract

The formation of a Bose condensate of magnons in a perpendicularly magnetized film of yttrium iron garnet under radio-frequency pumping in a strip line is studied experimentally. The characteristics of nonlinear magnetic resonance and the spatial distribution of the Bose condensate of magnons in the magnetic field gradient are investigated. In these experiments, the Bosonic system of magnons behaves similarly to the Bose condensate of magnons in the antiferromagnetic superfluid 3He-B, which was studied in detail earlier. Magnonic BEC forms a coherently precessing state with the properties of magnonic superfluidity. Its stability is determined by the repulsive potential between excited magnons, which compensates for the inhomogeneity of the magnetic field.