Magnonic Analogue of Edelstein Effect in Antiferromagnetic Insulators

TL;DR

This paper develops a linear response theory for temperature-gradient-induced spin polarization in antiferromagnetic insulators, revealing significant spin densities that could be experimentally observed, analogous to the Edelstein effect in electronic systems.

Contribution

It introduces a novel theoretical framework for magnonic spin polarization due to temperature gradients in antiferromagnets, including extrinsic and intrinsic effects, and applies it to various noncentrosymmetric materials.

Findings

Predicted large spin densities under realistic temperature gradients.

The response tensors align with magnetic symmetry expectations.

Potential for experimental detection of the effect.

Abstract

We investigate the nonequilibrium spin polarization due to a temperature gradient in antiferromagnetic insulators, which is the magnonic analogue of the inverse spin-galvanic effect of electrons. We derive a linear response theory of a temperature-gradient-induced spin polarization for collinear and noncollinear antiferromagnets, which comprises both extrinsic and intrinsic contributions. We apply our theory to several noncentrosymmetric antiferromagnetic insulators, i.e., to a one-dimensional antiferromagnetic spin chain, a single layer of kagome noncollinear antiferromagnet, e.g., $\text{KFe}_3(\text{OH})_6(\text{SO}_4)_2$, and a noncollinear breathing pyrochlore antiferromagnet, e.g., LiGaCr$_4$O$_8$. The shapes of our numerically evaluated response tensors agree with those implied by the magnetic symmetry. Assuming a realistic temperature gradient of $10 \text{K}/\text{mm}$, we find two-dimensional spin densities of up to $\sim 10^6\hbar/\text{cm}^2$ and three-dimensional bulk spin densities of up to $\sim 10^{14}\hbar/\text{cm}^3$, encouraging an experimental detection.