Spin Nernst effect in the Paramagnetic Regime of An Antiferromagnetic Insulator

TL;DR

This paper theoretically demonstrates that a pure spin Hall current, driven by a temperature gradient, can be generated in a paramagnetic antiferromagnetic insulator due to Dzyaloshinskii-Moriya interaction, even without magnetic order.

Contribution

It reveals that Dzyaloshinskii-Moriya interaction induces spin Nernst effect in paramagnetic insulators, extending previous understanding limited to magnetically ordered states.

Findings

Dzyaloshinskii-Moriya interaction enables spin Nernst effect without magnetic order.

Temperature dependence of SNE calculated using Schwinger boson mean-field theory.

Implications discussed for experimental realization of spin Nernst effect in paramagnetic insulators.

Abstract

We theoretically investigate a pure spin Hall current driven by a longitudinal temperature gradient, i.e., the spin Nernst effect (SNE), in a paramagnetic state of a collinear antiferromagnetic insulator with the Dzyaloshinskii-Moriya interaction. The SNE in a magnetic ordered state in such an insulator was proposed by Cheng {\it et al.} [R. Cheng, S. Okamoto, and D. Xiao, Phys. Rev. Lett. 117, 217202 (2016)]. Here we show that the Dzyaloshinskii-Moriya interaction can generate a pure spin Hall current even without magnetic ordering. By using a Schwinger boson mean-field theory, we calculate the temperature dependence of SNE in a disordered phase. We also discuss the implication of our results to experimental realizations.