Hybrid Dyons, inverted Lorentz force and magnetic Nernst effect in quantum spin ice

TL;DR

This paper reveals that in quantum spin ice, emergent magnetic charges carry native electric charge, leading to novel electromagnetic effects such as an inverted Lorentz force and a magnetic Nernst effect, with potential experimental signatures.

Contribution

It uncovers the electric charge of emergent magnetic charges in quantum spin ice and explores their implications for electromagnetic responses and experimental detection.

Findings

Emergent magnetic charges carry native electric charge.

Electric fields induce emergent magnetic fields affecting charges.

Thermal gas of magnetic charges influences optical conductivity.

Abstract

Topological magnets host two sets of gauge fields: that of native Maxwell electromagnetism, thanks to the magnetic dipole moment of its constituent microscopic moments; and that of the emergent gauge theory describing the topological phase. Here, we show that in quantum spin ice, the emergent magnetic charges of the latter carry native electric charge of the former. We both provide a general symmetry-based analysis underpinning this result, and discuss a microscopic mechanism which binds a native electric charge to the emergent magnetic one. This has important ramifications. First and foremost, an applied electric field gives rise to an emergent magnetic field. This in turn exerts an `inverted' Lorentz force on moving emergent electric/native magnetic charges. This can be probed via what we term a magnetic Nernst effect: applying an electric field perpendicular to a temperature gradient yields a magnetisation perpendicular to both. Finally, and importantly as a further potential experimental signature, a thermal gas of emergent magnetic charges will make an activated contribution to the optical conductivity at low temperatures.