Magnetic Field Effect on Spin-Polarized Excitons in Two-Dimensional Cesium Lead Bromide Perovskites

Spin–orbital coupling (SOC) in asymmetric two-dimensional semiconductors exhibits the Rashba effect. This coupling also shows spin-selective electric and optical properties, which are crucial for spintronic applications. Herein, we report the behavior of large circularly polarized excitonic photoluminescence in a two-dimensional lead halide perovskite in a magnetic field. The degree of circular polarization was found to be anisotropic and also dependent on the number of atomic layers, with saturation values of 31 and 3.5% at 4.2 and 200 K, respectively. The results were well simulated through theoretical calculations, where stronger Rashba SOC induced higher circular polarization in an external magnetic field. This high circular polarization at elevated temperatures, combined with the high light-emission efficiency, highlights the application potential of perovskite semiconductors in spin-photonic devices.