Spin-Superfluidity and Spin-Current Mediated Non-Local Transport

Some strategies for reducing energy consumption in information processing devices involve the use of spin rather than charge to carry information. This idea is especially attractive when the spin current is a collective one carried by the condensate of a magnetically ordered state, rather than a quasiparticle current carried by electrons or magnons. In this Chapter we explain how easy-plane magnets can be viewed as Bose-Einstein condensates of magnons, defined in terms of quanta of the spin-component perpendicular to the easy plane, and how they can carry dissipationless spin-currents that induce non-local interactions between electrically isolated conducting channels. We comment specifically on important differences between superconductivity in normal/superconducting/normal circuits and spin-superfluidity in normal/magnetic/normal circuits.