Proximity-induced spin-orbit effects in graphene on Au

We introduce a pz-d coupling model Hamiltonian for the π-graphene/Au bands that predicts a rather large intrinsic spin-orbit (SO) coupling as is being reported in recent experiments and DFT studies. Working within the analytical Slater-Koster tight-binding approach we were able to identify the overlapping orbitals of relevance in the enhancement of the SO coupling for both the sublattice symmetric (BC) and the ATOP (AC) stacking configurations. Our model effective Hamiltonian reproduces quite well the experimental spectrum for the two registries, and in addition, it shows that the hollow site configuration (BC), in which the A/B sites remain symmetric, yields the larger increase of the SO coupling. We also explore the Au-diluted case keeping the BC configuration and show that it renders the preservation of the SO gap with a similar SO interaction enhancement as the undiluted case but with a smaller graphene-gold distance.