Two-dimensional Square Buckled Rashba Lead Chalcogenides

TL;DR

This paper introduces a lead sulphide monolayer as a 2D semiconductor exhibiting a large, strain-tunable Rashba spin-orbit effect, with potential for designing materials with controllable spin properties.

Contribution

It demonstrates the presence of a large Rashba effect in buckled PbS monolayers and provides a theoretical framework for manipulating spin textures via strain.

Findings

Large Rashba parameters at M and Γ points.

Strain can tune the Rashba effect and spin texture.

Density functional theory supports the tight-binding model.

Abstract

We propose the lead sulphide (PbS) monolayer as a 2D semiconductor with a large Rashba-like spin-orbit effect controlled by the out-of-plane buckling. The buckled PbS conduction band is found to possess Rashba-like dispersion and spin texture at the $M$ and $\Gamma$ points, with large effective Rashba parameters of $\lambda\sim5~$eV$\AA~$ and $\lambda\sim1~$eV$~\AA$, respectively. Using a tight-binding formalism, we show that the Rashba effect originates from the very large spin-orbit interaction and the hopping term that mixes the in-plane and out-of-plane $p$ orbitals of Pb and S atoms. The latter, which depends on the buckling angle, can be controlled by applying strain to vary the spin texture as well as the Rashba parameter at $\Gamma$ and $M$. Our density functional theory results together with tight-binding formalism provide a unifying framework for designing Rashba monolayers and for manipulating their spin properties.