Chemical strain induced Rashba effect in two-dimensional Ruddlesden-Popper perovskites

We report the observation of Rashba splitting in multilayer Cs$_2$⁢PbI$_2$⁢⁢Cl$_2$⁢ two-dimensional Ruddlesden-Popper phase perovskite nanocrystals (NCs) induced by chemical strain. Magnetic circular dichroism measurements reveal significant Zeeman splitting, indicating strong spin-orbit coupling. At 10 K, pronounced circular dichroism signals suggest structural asymmetry linked to the Rashba effect. Photoluminescence (PL) peak splitting at low temperatures, supported by polarization-dependent PL measurements showing emission anisotropy below 70 K, confirms the presence of spin selectivity. High-resolution synchrotron x-ray diffraction and temperature-dependent Raman data reveal a transition in unit cell parameters and phonon frequencies around 70 K, respectively, correlating with optical data. The strain induced local asymmetry facilitates these effects. Density functional theory calculations validate the experimental findings, showing clear spin splitting in the valence and conduction bands. This study investigates the influence of chemical strain on asymmetry-induced phenomena, such as the Rashba effect in Cs$_2$⁢⁢PbI$_2$⁢⁢Cl$_2$⁢ NCs, highlighting their potential as a promising platform for advanced technologies.