Ir(111) Surface State with Giant Rashba Splitting Persists under Graphene in Air

We reveal a giant Rashba effect (alpha(R) approximate to 1.3 eV angstrom) on a surface state of Ir(111) by angle-resolved photoemission and by density functional theory. It is demonstrated that the existence of the surface state, its spin polarization, and the size of its Rashba-type spin-orbit splitting remain unaffected when Ir is covered with graphene. The graphene protection is, in turn, sufficient for the spin-split surface state to survive in ambient atmosphere. We discuss this result along with indications for a topological protection of the surface state.