Recent investigations on the dipolar-octupolar compounds ${\mathrm{Ce}}_2{\mathrm{Zr}}_2{\mathrm{O}}_7$ and ${\mathrm{Ce}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$ 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 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.

• Received 18 January 2023
• Revised 14 June 2023
• Accepted 12 January 2024

DOI:https://doi.org/10.1103/PhysRevLett.132.066502