Rashba and Dresselhaus effects in two-dimensional Pb-I-based perovskites

Bulk hybride halide perovskites are governed by significant Rashba and Dresselhaus splitting. This indicates that such effects will not only affect their optoelectronic properties, but also those of their two-dimensional layered relatives. This work aims at understanding how different ways of symmetry breaking influence these effects in those materials. For this purpose, model structures are adopted where the organic compounds are replaced by Cs atoms. Disregarding possible distortions in the inorganic layers, results in structures with composition ${\mathrm{Cs}}_{n+1}{\mathrm{Pb}}_{n}{\mathrm{I}}_{3n+1}$. Using the all-electron full-potential density-functional-theory code exciting, the impact of atomic displacement on the band structure is systematically studied for $n=1$, 2, 3, and $\ensuremath{\infty}$. The displacement patterns that yield Rashba or Dresselhaus splitting are identified, and the amount of the splitting is determined as a function of displacement. Furthermore, the spin textures in the electronic states around the band gap are analyzed to differentiate between Rashba and Dresselhaus effects. This study reveals in-plane Pb displacements as the origin of the strongest effects.