# Observation of spin superfluidity: YIG magnetic films and beyond

## TL;DR

This paper discusses the theoretical possibility of spin superfluidity in YIG magnetic films, clarifies misconceptions about experimental evidence, and emphasizes that spin superfluidity in magnetically ordered solids remains unconfirmed.

## Contribution

It demonstrates that dynamical barriers can exist for spin supercurrents in YIG films and critiques recent experimental claims of observing spin superfluidity.

## Key findings

- Dynamical barriers can prevent spin supercurrents until a critical phase gradient.
- Recent experimental claims of spin superfluidity in YIG and antiferromagnets are not justified.
- Spin superfluidity in magnetically ordered solids has not been experimentally confirmed.

## Abstract

From topology of the order parameter of the magnon condensate observed in yttrium-iron-garnet (YIG) magnetic films one must not expect energetic barriers making spin supercurrents metastable. But we show that some barriers of dynamical origin are possible nevertheless until the gradient of the phase (angle of spin precession) does not exceed the critical value (analog of the Landau critical velocity in superfluids). On the other hand, recently published claims of experimental detection of spin superfluidity in YIG films and antiferromagnets are not justified, and spin superfluidity in magnetically ordered solids has not yet been experimentally confirmed.