The Relationship between Structural Distortions and Spin-splitting in Perovskites*

Hybrid metal halide perovskites have emerged as promising optoelectronic materials and are potential hosts of Rashba/Dresselhaus spin-splitting for spin-selective transport and spin-orbitronics. Using a first-principles approach combined with targeted experiments, we here address the microscopic factors that control the spin-splitting magnitude in perovskite systems. By investigating a broad array of chiral and achiral two-dimensional hybrid organic-inorganic perovskites (2D HOIPs), we first demonstrate that a specific bond angle disparity connected with asymmetric tilting distortion of the metal halide octahedra breaks "local" inversion symmetry and strongly correlates with the computed spin-splitting. This distortion metric can serve as a crystallographic descriptor for 2D HOIP selection with significant spin splitting. We next investigate the impact of chiral nanoligand arrangements at slab models of perovskite interfaces, indicative of perovskite nanocrystal (PNC) surfaces. Similar asymmetric tilting distortions can penetrate up to five inorganic layers into the PNCs, potentially connecting to quantum-well-like frontier orbitals located in the deeper layers of PNCs.