Topological Magnons on the Ferromagnetic Zigzag Lattice

TL;DR

This paper investigates the topological properties of magnon band structures in ferromagnetic zigzag lattices, revealing phases with chiral edge states that are robust against defects, using linear spin-wave theory.

Contribution

It introduces a comprehensive analysis of magnon topology in zigzag ferromagnets, including effects of anisotropic exchanges and Dzyaloshinskii-Moriya interactions, identifying new topologically nontrivial phases.

Findings

Identification of topologically nontrivial magnon phases with chiral edge states

Mapping of magnon band topology across a phase diagram

Robustness of edge states against elastic defect scattering

Abstract

Motivated by the experimental identification of magnetic compounds consisting of zigzag chains, we analyze the band structure topology of magnons in ferromagnets on a zigzag lattice. We account for the general lattice geometry by including spatially anisotropic Heisenberg exchange interactions and by Dzyaloshinskii-Moriya interaction on inversion asymmetric bonds. Within the linear spin-wave theory, we find two magnon branches, whose band structure topology (i.e., Chern numbers) we map out in a comprehensive phase diagram. Notably, besides topologically trivial and gapless phases, we identify topologically nontrivial phases that support chiral edge magnons. We show that these edge states are robust against elastic defect scattering.