Nonreciprocal Magnon by Symmetric Anisotropic Exchange Interaction in Honeycomb Antiferromagnet

TL;DR

This paper reveals a new microscopic mechanism for nonreciprocal magnons in honeycomb antiferromagnets, driven by symmetric anisotropic exchange interactions rather than Dzyaloshinskii-Moriya interactions, with tunable magnetic-field responses.

Contribution

It introduces a novel origin of nonreciprocal magnons based on symmetric anisotropic exchange interactions, expanding understanding beyond Dzyaloshinskii-Moriya-based mechanisms.

Findings

Nonreciprocal magnons arise from symmetric anisotropic exchange interactions.

Magnetic field can manipulate the nonreciprocal direction.

Results relate to magnetic toroidal multipoles.

Abstract

We investigate a microscopic origin of nonreciprocal magnon that is distinct from the Dzyaloshinskii-Moriya interaction in a honeycomb antiferromagnet. The key ingredient is a symmetric anisotropic exchange interaction depending on the bond direction, which results in a valley-type nonreciprocal magnon excitations under the staggered antiferromagnetic ordering. Furthermore, we find this type of nonreciprocal magnon exhibits a peculiar magnetic-field response; the nonreciprocal direction can be manipulated by the in-plane rotating magnetic field. The obtained results can be accounted for the emergence of the magnetic toroidal multipoles.