LAUSR

Abstract In this study we investigate the role of coupling between surface orbitals in a giant spin splitting (GSS) observed in the Pb/Ge(111)-1  ×  1 adsorption system along Γ − M − Γ ′ . We report, based on the density functional theory that, the magnitude of the GSS depends on the bonding structure of the Pb/Ge interface, varying from 242 to 667 meV for the metallic surface bands. The splitting is shown to be SOC enhanced, with  ∼ 93% of the effect being of SOC origin. The split-energy difference observed in the system is a result of a different coupling strength between px/py(Pb) and pz(Pb) orbitals, which produces corresponding values of unquenched orbital angular momentum. The described spin-split pattern corresponds to those observed in Tl/Si(111)-1  ×  1, Bi/Si(111)-( 3 × 3 ) R 30 ∘ , and 4/3ML Pb/Ge(111)-( 3 × 3 ) R 30 ∘ , which suggests that, their GSS may also be SOC enhanced.