Rashba band splitting in two-dimensional Ruddlesden–Popper halide perovskites

Due to the presence of heavy elements and the dynamic nature of hybrid halide perovskites, the strong spin–orbit coupling effect can give rise to Rashba band splitting in these materials. Despite many reports on the Rashba effect in 3D perovskites like CH₃NH₃PbI₃, little is known about its presence in two-dimensional Ruddlesden–Popper (2DRP) perovskites. In this work, we use first-principle calculations to investigate the magnitude and origin of the Rashba effect in three families of 2DRP perovskites. We demonstrate the correlation between the splitting magnitude and the octahedron distortions. Moreover, different numbers of inorganic layers, spacer cations, and A-site cations have a great influence on the Rashba splitting through different mechanisms. While structures with C₆H₅C₂H₄NH₃ (PEA) have a significant Rashba splitting only in the monolayer condition, C₄H₉NH₃ (BA) induces large distortion by tilting the CH₃NH₃ (MA) cations around all octahedrons, giving rise to a larger Rashba splitting with an increasing number of inorganic layers. Our work elucidates the magnitude and origin of the Rashba splitting in 2DRP perovskites and provides guidelines for the manipulation of the Rashba splitting in these materials.