Exceptional spin wave dynamics in an antiferromagnetic honeycomb lattice

TL;DR

This paper theoretically explores how electric currents influence spin wave behavior in an antiferromagnetic honeycomb lattice, revealing non-Hermitian topological phenomena and potential for magnon manipulation.

Contribution

It introduces a comprehensive theoretical framework showing current-induced reciprocal and nonreciprocal effects on spin waves, leading to novel non-Hermitian topological phenomena in antiferromagnetic systems.

Findings

Identification of reciprocal and nonreciprocal current-induced torques

Prediction of spin wave Doppler effect due to reciprocal terms

Discovery of non-Hermitian topological phenomena like exceptional points

Abstract

We theoretically investigate possible effects of electric current on the spin wave dynamics for the N\'{e}el-type antiferromagnetic order in a honeycomb lattice. Based on a general vector decomposition of the spin polarization of conduction electrons, we find that there can exist reciprocal and nonreciprocal terms in the current-induced torque acting on the local spins in the system. Furthermore, we show that the reciprocal terms will cause the spin wave Doppler effect, while the nonreciprocal terms can induce rich non-Hermitian topological phenomena in the spin wave dynamics, including exceptional points, bulk Fermi arc, non-Hermitian skin effect, etc. Our results indicate the capability to manipulate non-Hermitian magnons in magnetic materials by electric current, which could be important for both fundamental physics and technology applications.