Circular photogalvanic spectroscopy of Rashba splitting in 2D hybrid organicinorganic perovskite multiple quantum wells
Xiaojie Liu, Ashish Chanana, Uyen Huynh, Fei Xue, Paul M. Haney, Steve Blair, Xiaomei Jiang, Valy Vardeny
The two-dimensional (2D)-phenylethyl ammonium lead iodide (2D-PEPI) is an exemplary hybrid organic-inorganic halide perovskite, possessing large spin-orbit coupling and forming multiple quantum wells (MQW). We have used helicity-dependent steady state photocurrent and THz transient emission to study the circular photogalvanic effect (CPGE) in 2D-PEPI single crystal. Our findings confirm the existence of Rashba spin splitting in the continuum bands of 2D-PEPI due to structural inversion symmetry breaking that is mostly perpendicular to the multilayer planes. The CPGE action spectrum shows two separate features that are due to free carriers and excitons. With above gap excitation, the CPGE is generated via spin-polarized hot photocarriers whose spins are split in momentum space due to the Rashba effect; this is well explained by a four-band model calculation using Rashba splitting energy of 3010 meV. In contrast, the novel CPGE response of the excitons originates from the existence of resonant circular reflectivity in 2D-PEPI, which upon exciton dissociation leads to spin dependent photocarriers density.