# Thermal Hall Effect Induced by Magnon-Phonon Interactions

## TL;DR

This paper introduces a novel mechanism for the thermal Hall effect driven by magnon-phonon interactions, applicable in systems where mirror symmetry is broken, and demonstrates its significance in a specific ferromagnetic model.

## Contribution

It reveals a general symmetry-based mechanism for the thermal Hall effect induced by magnon-phonon coupling, supported by a concrete ferromagnetic model example.

## Key findings

- Thermal Hall conductivity is influenced by magnon-phonon anti-crossing points.
- The effect is comparable in magnitude to magnon-mediated thermal Hall effects.
- Symmetry breaking via mirror symmetry influences the thermal Hall response.

## Abstract

We propose a new mechanism for the thermal Hall effect in exchange spin-wave systems, which is induced by the magnon-phonon interaction. Using symmetry arguments, we first show that this effect is quite general, and exists whenever the mirror symmetry in the direction of the magnetization is broken. We then demonstrate our result in a collinear ferromagnet on a square lattice, with perpendicular easy-axis anisotropy and Dzyaloshinskii-Moriya interaction from mirror symmetry breaking. We show that the thermal Hall conductivity is controlled by the resonant contribution from the anti-crossing points between the magnon and phonon branches, and estimate its size to be comparable to that of the magnon mediated thermal Hall effect.