# Topological Magnon-Phonon Hybrid Excitations in Two-Dimensional Ferromagnets with Tunable Chern Numbers

## TL;DR

This paper theoretically demonstrates that magnon-phonon hybrid excitations in two-dimensional ferromagnets can have tunable topological properties, with potential experimental detection via thermal Hall conductivity.

## Contribution

It reveals the topological nature of magnon-polaron bands in 2D ferromagnets and shows how external magnetic fields can control their Chern numbers.

## Key findings

- Magnon-polaron bands are topologically nontrivial with finite Chern numbers.
- External magnetic fields can tune the Chern numbers and band-crossing lines.
- Thermal Hall conductivity can serve as an experimental probe for these topological excitations.

## Abstract

We theoretically investigate magnon-phonon hybrid excitations in two-dimensional ferromagnets. The bulk bands of hybrid excitations, which are referred to as magnon-polarons, are analytically shown to be topologically nontrivial, possessing finite Chern numbers. We also show that the Chern numbers of magnon-polaron bands and the number of band-crossing lines can be manipulated by an external magnetic field. For experiments, we propose to use the thermal Hall conductivity as a probe of the finite Berry curvatures of magnon-polarons. Our results show that a simple ferromagnet on a square lattice supports topologically nontrivial magnon-polarons, generalizing topological excitations in conventional magnetic systems.