Spectroscopic signatures of fractionalization in octupolar quantum spin ice

TL;DR

This paper predicts distinctive spectroscopic signatures in neutron scattering experiments that would confirm the existence of a novel $ ext{ extpi}$-flux octupolar quantum spin ice phase, a type of quantum spin liquid.

Contribution

It provides the first detailed theoretical prediction of measurable neutron scattering signatures for the $ ext{ extpi}$-flux octupolar quantum spin ice phase using an extended gauge mean-field approach.

Findings

Predicted a broad continuum with three peaks in the dynamical spin structure factor.

Identified energy-modulated rod motifs in neutron scattering signals.

Provided theoretical support for experimental detection of $ ext{ extpi}$-O-QSI.

Abstract

Recent investigations on the dipolar-octupolar compounds Ce$_2$Zr$_2$O$_7$ and Ce$_2$Sn$_2$O$_7$ suggest that they may stabilize so-called $\pi$-flux octupolar quantum spin ice ($\pi$-O-QSI), a novel three-dimensional quantum spin liquid hosting emergent photons. Confirmation of such an exotic phase would require the prediction of a distinctive signature and its subsequent experimental observation. So far, however, theoretical predictions for any such sharp smoking-gun signatures are lacking. In this Letter, we thoroughly investigate O-QSI using an extension of gauge mean-field theory. This framework produces a phase diagram consistent with previous studies and an energy-integrated neutron scattering signal with intensity-modulated rod motifs, as reported in experiments and numerical studies. We predict that the dynamical spin structure factor of $\pi$-O-QSI is characterized by a broad continuum with three distinctive peaks as a consequence of the two mostly flat spinon bands. These three peaks should be measurable by high-resolution inelastic neutron scattering. Such spectroscopic signatures would be clear evidence for the realization of $\pi$-flux quantum spin ice.