Vibrational motions enhance spin splitting in the band structure of a chiral hybrid metal-halide perovskite

We used ab inito molecular dynamics (AIMD) to study the interplay between molecular chirality and thermal motions in the producing spin texture in the band structure of several A₂PbI₄-based Ruddlesen-Popper  (RP) perovskite structures. With chiral cations, density functional theory with spin-orbit coupling predicted very small spin splitting of the electronic energy bands for the equilibrium crystal. Configurations harvested from AIMD simulations, in contrast, showed large splitting of energy bands, with the orientation of the spin in each band varying as a function of wave vector. We observed that the splitting is modulated by the atomic thermal motions, with the band splitting and spin texture varying substantially for configurations separated by several hundred femtoseconds. The conduction band minimum was also observed to occur at different wave vectors and with different spin polarizations for different configurations, suggesting the possibility that spin selectivity in the transport of electrons through the material could be modulated by dynamical scattering of electrons as the polariazation and band minimum fluctuate in time. Implications of these results for the phenomenon of chirality induced spin selectivity will be discussed.