Polariton Spin Separation and Propagation by Rashba-Dresselhaus Spin-Orbit Coupling in an Anisotropic Two-Dimensional Perovskite Microcavity.

The separation and propagation of spin are vital to understanding spin-orbit coupling (SOC) in quantum systems. Exciton-polaritons, hybrid light-matter quasiparticles, offer a promising platform for investigating SOC in quantum fluids. By utilization of the optical anisotropy of materials, Rashba-Dresselhaus SOC (RDSOC) can be generated, enabling robust polariton spin transport. However, the intrinsic connection between the RDSOC and polariton spin evolution lacks an intuitive interpretation. Here, we demonstrate room-temperature exciton-polaritons with RDSOC in a microcavity containing anisotropic two-dimensional hybrid perovskites. We reveal that the RDSOC arises from geometric phase accumulation during polariton polarization evolution on the Poincaré sphere, which generates an effective gauge field and drives momentum-space spin splitting. By resonantly injecting polaritons, we achieve the generation, separation, and propagation of purer polariton spin states, i.e., a polariton spin Hall effect. Our findings establish geometric phases as the origin of intrinsic RDSOC, paving a feasible avenue for spin-selective control in perovskite-based photonic devices.