Magnetic field control of topological magnon-polaron bands in two-dimensional ferromagnets

TL;DR

This paper theoretically explores how magnetic field direction influences the topological properties of magnon-polaron bands in 2D ferromagnets, revealing controllable topological phase transitions and proposing thermal Hall conductivity as an experimental probe.

Contribution

It introduces a theoretical framework for controlling topological magnon-polaron bands via magnetic field orientation in 2D ferromagnets, considering all phonon modes.

Findings

Topological properties vary with magnetic field direction.

Multiple topological phase transitions are identified.

Thermal Hall conductivity can probe topological changes.

Abstract

We theoretically study magnon-phonon hybrid excitations in a square lattice ferromagnet subjected to a magnetic field by varying the field direction. The bulk bands of hybrid excitations, which are referred to as magnon-polarons, are investigated by considering all three phonon modes: vertical phonon, transverse phonon, and longitudinal phonon. We show that the topological proprieties of three hybridizations are different in terms of the Berry curvature and the Chern numbers. We also find that the topological properties of the bands can be controlled by changing the direction of the magnetic field, exhibiting one or more topological phase transitions. The dependence of thermal Hall conductivity as a function of magnetic field direction is proposed as an experiment probe of our theoretical results.