Spin-Electric Coupling in Lead Halide Perovskites

Lead halide perovskites enjoy a number of remarkable optoelectronic properties. To explain their origin, it is necessary to study how electromagnetic fields interact with these systems. We address this problem here by studying two classical quantities: Faraday rotation and the complex refractive index in a paradigmatic perovskite CH3NH3PbBr3 in a broad wavelength range. We find that the minimal coupling of electromagnetic fields to the k center dot p Hamiltonian is insufficient to describe the observed data even on the qualitative level. To amend this, we demonstrate that there exists a relevant atomic-level coupling between electromagnetic fields and the spin degree of freedom. This spin-electric coupling allows for quantitative description of a number of previous as well as present experimental data. In particular, we use it here to show that the Faraday effect in lead halide perovskites is dominated by the Zeeman splitting of the energy levels and has a substantial beyond-Becquerel contribution. Finally, we present general symmetry-based phenomenological arguments that in the low-energy limit our effective model includes all basis coupling terms to the electromagnetic field in the linear order.

Automated summary

Lead halide perovskites have remarkable optoelectronic properties. To understand their origin, the interactions between electromagnetic fields and these systems are studied. The Faraday effect and complex refractive index in a paradigmatic perovskite CH3NH3PbBr3 are investigated, and it is found that the minimal coupling of electromagnetic fields to the k center dot p Hamiltonian alone is insufficient to explain the data. A relevant atomic-level coupling between electromagnetic fields and the spin degree of freedom is demonstrated to provide a quantitative description. The Faraday effect in lead halide perovskites is dominated by Zeeman splitting and has a significant beyond-Becquerel contribution.