Control spin-orbit coupling through changing the crystal structure of the metal halide perovskites

Metal halide perovskites (MHPs) have attracted wide interest in spintronics. In addition, they also perform various spin-orbit coupling (SOC) strength due to their complex crystal structures. The control of SOC strength has been an increasingly prevalent topic for the manipulation of the spin degree in spintronic devices. Here, we fabricate MAPbI(3) films possessing cubic crystal phase and tetragonal crystal phase with Pb vacancies. Circular photogalvanic effect (CPGE) measurements indicate that C-N, representing the difference between right and left circularly polarized photocurrents, of the tetragonal structure with Pb vacancies (C-N = 0.6316) is almost three orders of magnitude larger than that of the cubic structure (C-N = 0.0009). Combining with the density functional theory calculations, we confirm that the strength of SOC generating the CPGE could be tuned by crystal phases of MAPbI(3), and the existence of Pb vacancies could remarkably enhance the spin splitting of the band structure. Our finding provides a possible way for clarifying various puzzling SOC performances in MHPs and paves the way for spintronic device applications and circularly polarized photoelectric detectors by controlling the crystal phases and defects.