Ultrasound detection of emergent photons in generic quantum spin ice

TL;DR

This paper proposes ultrasound measurements as a new method to detect emergent photons in quantum spin ice phases, including challenging cases with octupolar components, by analyzing phonon spectrum renormalization.

Contribution

It introduces ultrasound as a novel experimental probe for emergent photons in various quantum spin ice phases, especially where neutron scattering is ineffective.

Findings

Ultrasound can detect the speed of emergent photons via phonon spectrum renormalization.

Ultrasound distinguishes between dipolar and octupolar quantum spin ice phases.

Theoretical analysis applies to non-Kramers and dipolar-octupolar compounds.

Abstract

Experimental identification of quantum spin ice (QSI), a U(1) quantum spin liquid on the pyrochlore lattice hosting emergent photons, is a major challenge in frustrated magnets. In this work, we propose ultrasound measurements as a novel tool for probing the emergent photons of various QSI phases. Our analysis includes QSI phases in non-Kramers doublet compounds such as $\rm{Pr}_2 \rm{Zr}_2 \rm{O}_7$ as well as dipolar-octupolar Kramers doublet compounds such as $\rm{Ce}_2 \rm{Zr}_2 \rm{O}_7$. The latter may host emergent photons associated with an octupolar component which renders them difficult to detect with inelastic neutron scattering. We demonstrate theoretically how the speed of the emergent photons can be obtained from the renormalization of the phonon spectrum and show that ultrasound measurements provide a means of distinguishing the dipolar from the octupolar QSI phase in dipolar-octupolar materials.