Circular photogalvanic spectroscopy of Rashba splitting in 2D hybrid organic\u2013inorganic perovskite multiple quantum wells

Xiaojie Liu,Xiaomei Jiang,Z. V. Vardeny,Paul Haney,Ashish Chanana,Uyen Huynh,Steve Blair,Fei Xue

doi:10.1038/s41467-019-14073-6

Abstract

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.

Highlights

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)
Using circularly polarized light excitation we obtained steady state spin-dependent photocurrent and ultrafast terahertz (THz) emission, which verify the existence of circular photogalvanic effect (CPGE) in 2D-PEPI single crystal multiple quantum wells (MQW)
The circular photogalvanic effect (CPGE) action spectrum contains two distinct features that are due to excitons and free carriers, respectively

Summary

Introduction

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. In the presence of structural inversion symmetry breaking, the SOC leads to spinsplitting of the continuum bands, a phenomenon known as ‘Rashba splitting’ (see Fig. 1d)[10,11,12,13,14]. This may open a new avenue of using HOIP in spin-related optoelectronic and spintronic applications[15,16,17]. Can be intercalated in the cube formed by eight cornersharing [MX6]4- octahedra. 2D HOIP offer superior stability over the 3D counterparts due to the protection of the hydrophobic organic layer, and tunability owing to the synthesis versatility[18,19,20]

Methods

Results

Conclusion