Giant Rashba-Spin Splitting of Bi(111) Bilayer on Large Band Gap $\beta -$In${}_2$Se${}_3$

Abstract

Experimentally it is still challenging to epitaxially grow Bi(111) bilayer (BL) on conventional semiconductor substrate. Here, we propose a substrate of $\beta -$In${}_2$Se${}_3$(0001) with van der Waals like cleavage and large band gap of 1.2~eV. We have investigated the electronic structure of BL on one quintuple-layer (QL) $\beta -$In${}_2$Se${}_3$(0001) using density functional theory calculation. It is found that the intermediate hybridization between BL and one QL $\beta -$In${}_2$Se${}_3$(0001) results in the formation of bands with giant Rashba spin splitting in the large band gap of the substrate. Furthermore the Rashba parameter ${\alpha }_R$ can be increased significantly by tensile strain of substrate. Our findings provide a good candidate substrate for BL growth to experimentally realize spin splitting Rashba states with insignificant effect of spin degenerate states from the substrate.