Identifying, and constructing, complex magnon band topology

TL;DR

This paper explores the classification and identification of topological magnon band structures in magnetic materials, proposing a symmetry-based approach to find topologically nontrivial magnon bands for spintronics.

Contribution

It adapts topological quantum chemistry methods to magnon bands, enabling efficient identification of topological magnon phases using symmetry data and elementary band representations.

Findings

Developed a symmetry-based framework for magnon band topology

Identified criteria for topological magnon bands using decomposable elementary band representations

Provided methods to detect symmetry-enforced nodal topologies in magnon spectra

Abstract

Magnetically ordered materials tend to support bands of coherent propagating spin wave, or magnon, excitations. Topologically protected surface states of magnons offer a new path towards coherent spin transport for spintronics applications. In this work we explore the variety of topological magnon band structures and provide insight into how to efficiently identify topological magnon bands in materials. We do this by adapting the topological quantum chemistry approach that has used constraints imposed by time reversal and crystalline symmetries to enumerate a large class of topological electronic bands. We show how to identify physically relevant models of gapped magnon band topology by using so-called decomposable elementary band representations, and in turn discuss how to use symmetry data to infer the presence of exotic symmetry enforced nodal topology.