Topological magnon modes on honeycomb lattice with coupling textures

TL;DR

This paper proposes a new method to realize topological magnon modes on honeycomb lattices using only nearest-neighbor exchange couplings, leading to robust magnon edge states with potential applications in information transport.

Contribution

It introduces a novel scheme for topological magnons on honeycomb lattices that relies solely on nearest-neighbor exchange couplings, with tunable interactions inducing topological states.

Findings

Topological magnon modes appear at interfaces with magnon currents.

Band inversion occurs between p- and d-orbital like magnon modes.

Magnon edge states exhibit spin-momentum locking similar to quantum spin Hall effect.

Abstract

Topological magnon modes are expected to be useful for novel applications such as robust information propagation, since they are immune to backscattering and robust against disorder. Although there are several of theoretical proposals for topological magnon modes and growing experimental efforts for realizing them by now, it is still desirable to add complementary insights on this important phenomenon. Here, we propose a new scheme to achieve topological magnon where only nearest-neighbour exchange couplings on honeycomb lattice are necessary. In both ferromagnets and antiferromagnets, tuning exchange couplings between and inside hexagonal unit cells induces a topological state accompanied by a band inversion between p-orbital and d-orbital like magnon modes. Topological magnon modes appear at the interface between a topological domain and a trivial domain with magnon currents, which counterpropagate depending on pseudospins originated from orbital angular momenta of magnon modes. This mimics the spin-momentum locking phenomenon in the quantum spin Hall effect.