Strong enhancement of spin–orbit splitting induced by σ–π coupling in Pb-decorated silicene

Abstract

Electronic properties and spin–orbit (SO) splitting of silicene adsorbed with Cu, Ag, Au and Pb atoms at different coverages are investigated by means of first-principles calculations. All four kinds of adatoms we studied tend to adsorb at hollow sites. The adsorption of Pb atoms enhances the hybridization of σ electrons and π electrons around the Fermi level in silicene, resulting in considerable SO splitting (∼100 meV). Only a small degree of SO splitting is achieved in NM–silicene (NM stands for noble metal atoms, i.e. Cu, Ag, and Au) systems. Our results suggest that the σ–π coupling is a very important factor for the enhancement of SO coupling in silicene. The concentration and the intrinsic SO coupling of adatoms will also affect SO splitting in these systems. All structures we studied are stable at room temperature. Our work provides an imperative understanding of the physical mechanism of enhancing SO coupling in two dimensional materials.