The two-dimensional (2D) Ruddlesden-Popper organic-inorganic halide perovskites such as (2D)-phenethylammonium lead iodide (2D-PEPI) have layered structure that resembles multiple quantum wells (MQW). The heavy atoms in 2D-PEPI contribute a large spin-orbit coupling that influences the electronic band structure. Upon breaking the inversion symmetry, a spin splitting ('Rashba splitting') occurs in the electronic bands. We have studied the spin splitting in 2D-PEPI single crystals using the circular photogalvanic effect (CPGE). We confirm the existence of Rashba splitting at the electronic band extrema of 35±10 meV, and identify the main inversion symmetry breaking direction perpendicular to the MQW planes. The CPGE action spectrum above the bandgap reveals spin-polarized photocurrent generated by ultrafast relaxation of excited photocarriers separated in momentum space. Whereas the helicity dependent photocurrent with below-gap excitation is due to spin-galvanic effect of the ionized spin-polarized excitons, where spin polarization occurs in the spin-split bands due to asymmetric spin-flip.

中文翻译：

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二维混合有机-无机钙钛矿多量子阱中Rashba分裂的圆形光电子能谱。

二维（2D）Ruddlesden-Popper有机-无机卤化物钙钛矿，例如（2D）-苯乙铵碘化铅（2D-PEPI），具有类似于多个量子阱（MQW）的分层结构。2D-PEPI中的重原子会产生较大的自旋轨道耦合，从而影响电子能带结构。打破反演对称性后，电子频带中发生自旋分裂（“ Rashba分裂”）。我们已经研究了使用圆形光电效应（CPGE）的2D-PEPI单晶体的自旋分裂。我们确认在35±10 meV的电子带极处存在Rashba分裂，并确定垂直于MQW平面的主要反演对称破坏方向。带隙上方的CPGE作用谱揭示了由动量空间中分离的激发光载流子的超快弛豫产生的自旋极化光电流。低于间隙激发的依赖于螺旋度的光电流是由于电离的自旋极化激子的自旋电流效应引起的，而由于不对称自旋翻转，自旋分裂带中发生自旋极化。