Rashba Band Splitting in CH3NH3PbI3: An Insight from Spin-Polarized Scanning Tunneling Spectroscopy.

Abstract

We report an experimental observation of Rashba splitting in methylammonium lead iodide (MAPbI3). Because of a large spin-orbit coupling parameter in the noncentrosymmetric material, both of the bands were predicted to split having two different spin-textures leading to two different Z-components of total angular momentum (JZ). We use spin-polarized scanning tunneling spectroscopy to probe only one-type of JZ-matched bands throughout the film; dI/dV spectra recorded at many different points of a film however allowed us to spot both the Rashba split-levels and also deliberate on their spin-textures. We observe that the bands split in such a manner that the conduction and valence bands closer to the Fermi energy have the same type of spin-textures (a spin-allowed transition model). Still a low recombination rate of photogenerated carriers in MAPbI3 has been analyzed by considering Wannier-type excitons, a molecular nature of spin-domains from dI/dV images, and therefore a spin-forbidden nature of interdomain transition.