Superfluid spin transport in ferro- and antiferromagnets
Prof. Edouard B. Sonin (Hebrew University of Jerusalem)

The talk addresses the phenomenon of spin superfluidity in magnetically ordered solids, which has already been discussed a number of decades. The theory of the phenomenon is based on the three concepts: topology of the order parameter space, the Landau criterion for superfluidity, and phase slips. The talk discusses the role of dissipation on the superfluid spin transport in bulk and on formation of the superfluid spin current near the interface where spin is injected. The Gilbert damping parameter in the Landau--Lifshitz--Gilbert theory does not describe dissipation properly, and the dissipation parameters are calculated from the Boltzmann equation for magnons scattered by defects. The two-fluid theory is developed similar to the two-fluid theory for superfluids. The influence of temperature variation in space on the superfluid spin transport (bulk Seebeck effect) is analysed within this theory. The experimental work on spin superfluidity is reviewed.