Topology-guided vortices in a polariton condensate.

A major challenge in polariton fluids is achieving deterministic control over the spin texture of the macroscopic condensate, which governs the nucleation and dynamics of topological excitations such as vortices, solitons and strings. Typically, external gauge fields are used to access the polariton pseudospin, resulting in configurations weakly constrained by cavity modes and sensitive to disorder and fluctuations. Here we report spin polaritons confined by the topology of a bound state in the continuum metasurface with broken inversion symmetry in a halide-perovskite film. Geometry-driven condensation under spin-momentum locking produces pairs of half-vortices with opposite spin, intrinsically pinned to polarization strings extending from their cores. By tuning excitation density, these half-vortices are controllably displaced along the strings, preventing annihilation across an interposed topological domain wall. This approach establishes cavity geometry as an intrinsic source of spin textures, guiding vortex displacement and enabling robust topological excitations in structurally disordered materials.