Spin Superfluidity in Biaxial Antiferromagnetic Insulators

TL;DR

This paper demonstrates that spin superfluidity can occur in biaxial antiferromagnetic insulators like NiO, especially near the spin-flop transition under high magnetic fields, enabling long-distance spin transport despite anisotropy barriers.

Contribution

It shows that spin superfluidity in antiferromagnetic insulators is achievable near the spin-flop transition, overcoming anisotropy barriers and enabling long-range spin transport.

Findings

Spin superfluidity is hindered by anisotropy but can be enabled near the spin-flop transition.

High magnetic fields remove the anisotropy-induced threshold for spin superfluidity.

Spin superfluidity persists over many micrometers even in dirty samples.

Abstract

Antiferromagnets may exhibit spin superfluidity since the dipole interaction is weak. We seek to establish that this phenomenon occurs in insulators such as NiO, which is a good spin conductor according to previous studies. We investigate nonlocal spin transport in a planar antiferromagnetic insulator with a weak uniaxial anisotropy. The anisotropy hinders spin superfluidity by creating a substantial threshold that the current must overcome. Nevertheless, we show that applying a high 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.