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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.
Science Advances
Created July 28, 2017, Updated November 10, 2018