Weyl magnons in pyrochlore antiferromagnets with all-in-all-out orders

TL;DR

This paper predicts the existence of Weyl magnons in pyrochlore antiferromagnets with all-in-all-out order under external magnetic fields or uniaxial strains, highlighting their robustness and experimental accessibility.

Contribution

It introduces the theoretical prediction of Weyl magnons in pyrochlore AIAO magnets under realistic conditions, expanding the understanding of topological magnons.

Findings

Weyl magnons can be realized in pyrochlore AIAO antiferromagnets with magnetic field or strain.

Minimal two Weyl points can be achieved, not previously observed.

Weyl magnons are robust against Dzyaloshinskii-Moriya interactions.

Abstract

We investigate novel topological magnon band crossings of pyrochlore antiferromagnets with all-in-all-out (AIAO) magnetic order. By general symmetry analysis and spin-wave theory, we show that pyrochlore materials with AIAO orders can host Weyl magnons under external magnetic fields or uniaxial strains. Under a small magnetic field, the magnon bands of the pyrochlore with AIAO background can feature two opposite-charged Weyl points, which is the minimal number of Weyl points realizable in quantum materials and has not be experimentally observed so far. We further show that breathing pyrochlores with AIAO orders can exhibit Weyl magnons upon uniaxial strains. These findings apply to any pyrochlore material supporting AIAO orders, irrespective of the forms of interactions. Specifically, we show that the Weyl magnons are robust against direct (positive) Dzyaloshinskii-Moriya interactions. Because of the ubiquitous AIAO orders in pyrochlore magnets including R$_2$Ir$_2$O$_7$, and experimentally achievable external strain and magnetic field, our predictions provide promising arena to witness the Weyl magnons in quantum magnets.