An efficient material search for room-temperature topological magnons

Abstract

Topologically protected magnon surface states are highly desirable as an ideal platform to engineer low-dissipation spintronics devices. However, theoretical prediction of topological magnons in strongly correlated materials proves to be challenging because the ab initio density functional theory calculations fail to reliably predict magnetic interactions in correlated materials. Here, we present a symmetry-based approach, which predicts topological magnons in magnetically ordered crystals, upon applying external perturbations such as magnetic/electric fields and/or mechanical strains. We apply this approach to carry out an efficient search for magnetic materials in the Bilbao Crystallographic Server, where, among 198 compounds with an over 300-K transition temperature, we identify 12 magnetic insulators that support room-temperature topological magnons. They feature Weyl magnons with surface magnon arcs and magnon axion insulators with either chiral surface or hinge magnon modes, offering a route to realize energy-efficient devices based on protected surface magnons.

KMg4Bi3: A Narrow Band Gap Semiconductor with a Channel Structure

“…The discovery of new intermetallic compounds containing Bi, the highest-spin orbit element with negligible radioactivity, is a growing vector in the search for quantum materials due to the presence of unique electronic, magnetic, and topological phenomena in these phases. − One such class of quantum materials that rely on the high-spin orbit coupling of Bi consists of topological insulators (TIs). , All semiconductors have surface states due to the interruption of the periodic potentials of the atoms in the bulk, which creates additional energy levels that are available to electrons at the surface. In materials with inverted electronic band energies, electrons in the surface states can be topologically protected from backscattering and can develop other unusual properties, making them topological insulators.…”

Entanglement-enabled symmetry-breaking orders

“…On the other hand, EESBO is intrinsically quantum, indicating the incompleteness of the above description. For instance, recent development in the systematic understanding of the magnon topological band structures is based on "classical" symmetry-breaking orders [6][7][8][9][10]. However, the complete understanding must incorporate the magnons arising from EESBOs.…”