Spin Nernst Effect of Magnons in Collinear Antiferromagnets

TL;DR

This paper predicts a spin Nernst effect of magnons in collinear antiferromagnets, where a temperature gradient induces opposite transverse magnon flows without thermal Hall current, influenced by magnon modes at different points in momentum space.

Contribution

It introduces the concept of a spin Nernst effect of magnons in antiferromagnets driven by temperature gradients, highlighting the role of magnon modes at different momentum points.

Findings

Magnons at Γ- and K-points contribute oppositely to spin transport.

The spin Nernst coefficient changes sign with temperature.

A vanishing thermal Hall current accompanies the effect.

Abstract

In a collinear antiferromagnet with easy-axis anisotropy, symmetry guarantees that the spin wave modes are doubly degenerate. The two modes carry opposite spin angular momentum and exhibit opposite chirality. Using a honeycomb antiferromagnet in the presence of the Dzyaloshinskii-Moriya interaction, we show that a longitudinal temperature gradient can drive the two modes to opposite transverse directions, realizing a spin Nernst effect of magnons with vanishing thermal Hall current. We find that magnons around the {\Gamma}-point and the K-point contribute oppositely to the transverse spin transport, and their competition leads to a sign change of the spin Nernst coefficient at finite temperature. Possible material candidates are discussed.