Recent Developments in Spin Superfluid Transport

Spin Superfluidity, also called Dissipative Exchange Flow to emphasize its distinguishing features from traditional superfluids, is coherent spin transport mediated by topological winding in the texture of a magnetic order parameter. Experimental signatures for Spin Superfluids have been observed in recent years, most notably in antiferromagnets and amorphous magnets; however, in some respects experimental progress has been surprisingly elusive, especially for ferromagnets. Experimental observation of ferromagnetic spin superfluids may require overcoming various problems, such as pinning due to the effective anisotropy induced by strong demagnetizing fields of thin films, as well as spin current screening due to soliton formation at the boundary. We discuss how some of these problems are actually features which lead to a rich and potentially useful non-equilibrium phase diagram. In addition, we show how spin superfluid signals could propagate through a 3D amorphous magnet, despite the spin superfluid being unstable due to a lack of barriers to phase slips.