Establish the collective-excitation spectrum of photonic supersolids

Establish the dispersion and driven-dissipative modifications of the collective excitation modes in supersolid states of light, resolving the lack of consensus among existing theoretical treatments and enabling direct experimental characterization.

Background

Supersolid states of light simultaneously break condensate-phase and translational symmetries, so they are expected to possess multiple collective modes. Initial theoretical studies have begun to address these modes, but the review states that the basic structure of their dispersion and the effects of driving and dissipation remain unsettled. The authors identify spectroscopic measurements analogous to those used for spatially uniform fluids as a route toward resolving the issue.

References

Concerning collective excitations, first theoretical steps are appearing in the literature, but no consensus has yet been reached on the basic features of their dispersion and, in particular, on the impact of the driven-dissipative nature on them.

— Collective excitations of driven-dissipative quantum fluids of light  (2609.40110 - Bramati et al., 30 Sep 2026) in Section 8.1, subsection “Open questions”

As an additional feature that is still awaiting experimental observation, the theoretical calculations also predict that the gap can now appear either in the imaginary part or in both the real and the imaginary parts of the dispersion.

— Collective excitations of driven-dissipative quantum fluids of light  (2609.40110 - Bramati et al., 30 Sep 2026) in Section 5.3, subsection “Driven-dissipative condensates”