Spin superfluidity

Abstract

The phenomenon of superfluidity (superconductivity) is a possibility of transport of mass (charge) on macroscopical distances without essential dissipation. In magnetically ordered media with easy-plane topology of the order parameter space the superfluid transport of spin is also possible despite the absence of the strict conservation law for spin. The article addresses three key issues in the theory of spin superfluidity: topology of the order parameter space, Landau criterion for superfluidity, and decay of superfluid currents via phase slip events, in which magnetic vortices cross current streamlines. Experiments on detection of spin superfluidity are also surveyed.