Dynamical Axions in $U(1)$ Quantum Spin Liquids

TL;DR

This paper proposes a new way to realize axions in quantum spin liquids, predicting measurable dynamical responses in candidate materials through their coupling to emergent electromagnetic fields.

Contribution

It introduces a novel mechanism for axion realization in quantum spin liquids and identifies experimental signatures in candidate pyrochlore materials.

Findings

Axions can couple to both external and emergent electromagnetic fields in spin liquids.

The interaction leads to a distinctive dynamical response detectable via inelastic neutron scattering.

Provides a pathway to study axion electrodynamics in frustrated magnetic systems.

Abstract

Since their proposal nearly half a century ago, physicists have sought axions in both high energy and condensed matter settings. Despite intense and growing efforts, to date experimental success has been limited, with the most prominent results arising in the context of topological insulators. Here we propose a novel mechanism whereby axions can be realized in quantum spin liquids. We discuss the necessary symmetry requirements and identify possible experimental realizations in candidate pyrochlore materials. In this context, the axions couple both to the external and to the emergent electromagnetic fields. We show that the interaction between the axion and the emergent photon leads to a characteristic dynamical response, which can be measured experimentally in inelastic neutron scattering. This work sets the stage for studying axion electrodynamics in the highly tunable setting of frustrated magnets.