Giant Rashba-Splitting in 2D organic-inorganic halide perovskites measured by transient spectroscopies
Yaxin Zhai, S. Baniya, C. Zhang, Junwen Li, Paul M. Haney, C.-X. Sheng, Z. Vardeny
Two-dimensional (2D) layered hybrid organic-inorganic halide perovskite semiconductors form natural multiple quantum wells that possess strong spin-orbit coupling due to the heavy elements in their building blocks. This may lead to Rashba-splitting close to the extrema in the electron bands. We have employed a plethora of ultrafast transient, nonlinear optical spectroscopies, and theoretical calculations for studying the primary (excitons) and longlived (free-carriers) photoexcitations in thin films of 2D perovskite, namely (C6H5C2H4NH3)2PbI4. The density functional theory calculation shows the occurrence of Rashba-splitting in the plane perpendicular to the 2D barrier. From the electroabsorption spectrum and photoinduced absorption spectra from excitons and free-carriers we indeed obtain a giant Rashba-splitting in this compound, with energy splitting of 40 meV ± 1 meV and Rashba parameter of 1.55 eV·Å ± 0.02 eV·Å; which are among the highest Rashba-splitting size parameters reported so far. This finding shows that 2D hybrid perovskites have great promise for potential applications in spintronics.