Origin of Giant Rashba Effect in Graphene on Pt/SiC

Intercalation of noble metals can produce giant Rashba-type spin-orbit splittings in graphene. The spin-orbit splitting of more than 100 meV has yet to be achieved in graphene on metal or semiconductor substrates. Here, we report the p-type graphene obtained by Pt intercalation of zero-layer graphene on SiC substrate. The spin splitting of similar to 200 meV was observed at a wide range of binding energies. Comparing the results of theoretical studies of different models with the experimental ones measured by spin-ARPES, XPS and STM methods, we concluded that inducing giant spin-orbit splitting requires not only a relatively close distance between graphene and Pt layer but also the presence of graphene corrugation caused by a non-flat Pt layer. This makes it possible to find a compromise between strong hybridization and increased spin-orbit interaction. In our case, the Pt submonolayer possesses nanometer-scale lateral ordering under graphene.