Spin Superfluidity in Uniaxial and Biaxial Antiferromagnetic Insulators

Antiferromagnets may exhibit spin superfluidity since there is no long-range dipole interaction. We seek to establish that this phenomenon occurs in typical insulators. We investigate non-local spin transport in two scenarios, a uniaxial antiferromagnet and a planar antiferromagnetic insulator with a weak easy-axis anisotropy. In these systems, the anisotropy hinders spin superfluidity by creating a substantial threshold that the current must overcome. Nevertheless, we show that applying a magnetic field removes this obstacle near the spin-flop transition of the antiferromagnet. Importantly, the spin superfluidity can then persist across many micrometers, even in dirty samples.