Towards Room-Temperature Exciton-Polariton Supersolidity Driven by Guided Optical Parametric Oscillation

Supersolidity is a counterintuitive quantum phase of matter where the long-range spatial order of a solid coexists with the frictionless flow characteristic of a superfluid. Recently, evidence of supersolidity has been demonstrated in polariton condensates in III-V photonic crystal microcavities by condensing into a topological bound state in the continuum, offering a new light-matter hybrid platform for exploring such quantum phase. In this work, we propose a theoretical scheme for realizing room-temperature supersolidity based on halide perovskite exciton polaritons operating in the optical parametric oscillation regime. By employing a waveguide microcavity geometry, we confine polariton scattering direction in reciprocal space, enabling controlled momentum selection. Leveraging the intrinsic nonlinear interactions among polaritons, we theoretically demonstrate the spontaneous breaking of both continuous translational symmetry and global phase symmetry, i.e., the evidence of supersolidity. Furthermore, we identify a tunable phase transition sequence in our system: from a Bose–Einstein condensate to a supersolid phase, and ultimately to an insulating phase, as the nonlinear interaction strength increases.