Orbital control of Rashba spin orbit coupling in noble metal surfaces
Rashba spin orbit coupling (SOC) in noble metal surfaces is of great importance for the application of metal films in spintronic devices. By combining the density-functional theory calculations with our recently developed orbital selective external potential method, we investigate the Rashba SOC in the Shockley surface states of Au(111) and Ag(111). We find that the large Rashba SOC in the sp-character surface states of Au(111) is mainly contributed by the minor d-orbitals in the surface states. While for the sd-character surface states, although they are dominated by the d-orbitals, Rashba splitting is found to be rather small. Band structure analysis reveals that this is mainly because the sd-character surface states are well below the Fermi level and can be less influenced by the asymmetric surface potential. We demonstrate that the Rashba SOC in noble metal surfaces can be effectively manipulated by shifting the d-orbitals in the surface states, which can be physically implemented through surface decoration. Our investigation provides a deep understanding on Rashba SOC in noble metal surfaces and could be helpful to their applications in spintronic devices.