Fig. 1. Rashba splitting in 2D hybrid organic–inorganic perovskite (2D-PEPI) crystal.
a Schematic of the 2D-PEPI structure with alternating (C6H5C2H4NH3+) and [PbI6]4− layers, which form natural multiple quantum wells (MQW), where the inorganic layer is the potential ‘well’ and organic layer is the potential ‘wall’. The potential values were taken from ref. 22 The crystal structure is triclinic at room temperature, with growth direction along the c-axis. b Room temperature absorption (black line) spectrum of a thin film 2D-PEPI where the exciton (EX) and interband (IB) transitions are denoted. The inset shows the reflectivity spectrum of a single crystal (blue symbol), having two different spectra features. The red(blue) broken line marks the two exciton species (EX1/EX2) observed in the 2D-PEPI crystal. c Experimental setup for measuring the PGE using λ/4 plate; the angles α, θ, and ϕ are denoted. x’ indicates the current flow direction, making an angle, ψ with the crystal a-axis. d Schematic diagram of the continuum bands (VB and CB) having Rashba spin splitting, and related optical transitions with circular polarized light. The electron group velocity (and current) change polarity when the light changes helicity. Ed is the direct energy difference between the CB and VB Dirac points.