Enhancing the Rashba spin splitting at X/Au/Si(111) surface by induced intrinsic spin-polarization

Abstract

Adsorbed/modified surface is usually treated as a prototype to study Rashba spin splitting. Using first-principles calculations and analyses, we first explain the Rashba spin splitting of monovalent alkali metal adsorbed on Au/Si(111) surface as realized in experiment. We clearly identify that Na adatom donates one electron to pristine Au/Si(111) surface, leading to the Fermi level shift upward to the parabolic range of Au d and Si p hybridized states and thus leading to large Rashba spin splitting in Na/Au/Si(111) system. However, for the larger intra-atomic spin-orbit coupling Cs adsorbate, it not only plays the identical role to Na adatom, but induces intrinsic spin-polarization surprisingly, which further enhances the Rashba spin splitting on the Cs/Au/Si(111) surface up to ∼200 meV. Our proposed mechanism that intrinsic spin-polarization significantly enhancing the Rashba spin splitting is generally applicable and can be extended readily to alkali-earth metal as epitaxial layer grown on Au/Si(111) surface.