Circularly Polarized Photoluminescence with Spin Selectivity Through Rashba Band Structures and Chiral Structures in Hybrid Perovskites

Circularly polarized photoluminescence (CPL) have been observed in organic-inorganic hybrid perovskites. In general, CPL require the orbital momentum in light-emitting states that can be circularly polarized by a photoexcitation and substantially conserved within PL lifetime. Both chiral structures and Rashba band structures can fulfill this requirement: generating circularly polarizable orbitals with sufficient conservation time constant to develop CPL. In chiral structures, our experimental studies found that light-emitting states establish chirality dynamics with ultrafast response (< picoseconds) and then conserve their circular polarization up to nanoseconds, enabling CPL. This provides a circular polarizer functionality in light emission shown in chiral structures. Furthermore, spin scattering between circularly polarized light-emitting states can shorten the conservation time constant of circularly polarized orbitals, decreasing CPL. This indicates that spin interaction between circularly polarized orbitals plays an important role in developing CPL. In Rashba band structures, we found that left-hand and right-hand circularly polarized orbitals can be optically operated between spin-up and spin-down bands to generate selective CPL by using circularly polarized photoexcitation. Moreover, we found that spin polarizations can directly interact with circularly polarized orbitals in Rashba band structures through spin-exchange coupling, generating spin-switchable phenomena in 2D-superlattice perovskites. This demonstrates switchable CPL between left-hand and right-hand circular polarizations when changing spin polarizations between positive and negative magnetic field directions. This indicates that the spin-exchange coupling functions as the key parameter towards developing CPL in Rashba band structures in hybrid perovskites.