Nonreciprocal spin Seebeck effect in antiferromagnets

TL;DR

This paper theoretically predicts a nonreciprocal spin Seebeck effect in antiferromagnets with broken inversion symmetry, revealing unique properties and potential for controlled spin current flow in these materials.

Contribution

It introduces the concept of nonreciprocal spin Seebeck effect in antiferromagnets and demonstrates how crystal symmetry influences nonreciprocity, including perfect nonreciprocity in polar antiferromagnets.

Findings

Polar antiferromagnets exhibit perfect nonreciprocity.

Nonreciprocity can be controlled by reversing magnetic domains.

Calculated spin Seebeck voltages for specific antiferromagnets.

Abstract

We theoretically propose a nonreciprocal spin Seebeck effect, i.e., nonreciprocal spin transport generated by a temperature gradient, in antiferromagnetic insulators with broken inversion symmetry. We find that nonreciprocity in antiferromagnets has rich properties not expected in ferromagnets. In particular, we show that polar antiferromagnets, in which the crystal lacks the spatial inversion symmetry, exhibit perfect nonreciprocity --- one-way spin current flow irrespective of the direction of the temperature gradient. We also show that nonpolar centrosymmetric crystals can exhibit nonreciprocity when a magnetic order breaks the inversion symmetry, and in this case, the direction of the nonreciprocal flow can be controlled by reversing the magnetic domain. As their representatives, we calculate the nonreciprocal spin Seebeck voltages for the polar antiferromagnet $\alpha$-Cu$_2$V$_2$O$_7$ and the honeycomb antiferromagnet MnPS$_3$, while varying temperature and magnetic field.