Magnon Thermal Hall Effect Induced By Symmetric Exchange Interaction

TL;DR

This paper uncovers how symmetric exchange interactions can induce the magnon thermal Hall effect, revealing new mechanisms and angular dependencies in magnon transport without relying on Dzyaloshinskii-Moriya interactions.

Contribution

It establishes generalized Onsager relations for magnons and shows symmetric exchange interactions alone can produce the magnon thermal Hall effect, removing the need for inversion symmetry breaking.

Findings

Symmetric exchange interactions support the magnon thermal Hall effect.

The magnon thermal Hall effect can occur without Dzyaloshinskii-Moriya interaction.

Thermal conductivity shows angular dependence on in-plane magnetization.

Abstract

By analyzing the spin-group symmetry of magnons, we establish two generalized Onsager's relations in the magnon thermal Hall effect, which reveals the rich and complicated structures of the magnon Berry curvature in the parameter space of different types of the exchange coupling. As an important consequence, we find that the diagonal and off-diagonal part of the symmetric anisotropic exchange coupling together can support the planar magnon thermal Hall effect without the DM interaction. This removes the local inversion-symmetry-breaking condition for generating the magnon thermal Hall effect. Moreover, we predict an exotic phenomenon that the thermal conductivity exhibits angular dependence with respect to the in-plane magnetization. Our work lays the ground for decoding the coupling between magnon transport and different types of exchange interactions.