Electric Field- and Strain-Induced Rashba Effect in Hybrid Halide Perovskites

Using first-principles density functional theory calculations, we show how Rashba-type energy band splitting in the hybrid organic-inorganic halide perovskites APbX₃ (A = CH₃NH₃⁺, CH(NH₂)₂⁺, Cs⁺, and X = I, Br) can be tuned and enhanced with electric fields and anisotropic strain. In particular, we demonstrate that the magnitude of the Rashba splitting of tetragonal (CH₃NH₃)PbI₃ grows with increasing macroscopic alignment of the organic cations and electric polarization, indicating appreciable tunability with experimentally feasible applied fields, even at room temperature. Further, we quantify the degree to which this effect can be tuned via chemical substitution at the A and X sites, which alters amplitudes of different polar distortion patterns of the inorganic PbX₃ cage that directly impact Rashba splitting. In addition, we predict that polar phases of CsPbI₃ and (CH₃NH₃)PbI₃ with R3c symmetry possessing considerable Rashba splitting might be accessible at room temperature via anisotropic strain induced by epitaxy, even in the absence of electric fields.