Topological magnons in Kitaev magnets with finite Dzyaloshinskii-Moriya interaction at high field

TL;DR

This paper investigates topological magnon excitations and thermal Hall effects in kagome magnets with Kitaev, Heisenberg, and Dzyaloshinskii-Moriya interactions under high magnetic fields, revealing phase transitions with opposite Chern numbers.

Contribution

It demonstrates the presence of topological magnon bands with nontrivial Chern numbers in a realistic model including DMI, and identifies phase transitions affecting thermal Hall conductivity.

Findings

Magnon bands have nontrivial Chern numbers in the polarized phase.

Phase transitions cause sign changes in thermal Hall conductivity.

DMI influences the width of topological phases.

Abstract

There have been intensive studies on Kitaev materials for the sake of the realization of exotic states such as quantum spin liquid and topological orders. In realistic materials, the Kitaev interaction may coexist with the Dzyaloshinskii-Moriya interaction (DMI), and it is a challenge to distinguish their magnitudes separately. Here, we study the topological magnon excitations and related thermal Hall conductivity of kagome magnet exhibiting Heisenberg, Kitaev and DM interactions exposed to a magnetic field. In a strong magnetic field perpendicular to the plane of the lattice ([111] direction) that bring the system into the fully polarized paramagnetic phase, we find that the magnon bands carry nontrivial Chern numbers in the full region of the phase diagram. Furthermore, there are phase transitions relate two topological phases with opposite Chern numbers, which lead to the sign changes of the thermal Hall conductivity. In the phase with negative thermal conductivity, the Kitaev interaction is relatively large and the width of the phase increases with the strength of DMI. Hence the study here will contribute to the understanding of related compounds.