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.