Spectroscopic Signatures of Fractionalization in Octupolar Quantum Spin Ice

Recent investigations on the dipolar-octupolar compounds Ce2Zr2O7 and Ce2Sn2O7 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 work 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.