Orbital selective coupling between Ni adatoms and graphene Dirac electrons

We investigate the coupling of Ni monomers and trimers to graphene by means of atomically resolved scanning tunneling microscopy (STM). The precise adsorption site of the adatoms is determined experimentally. STM images reveal characteristic nodal structures above the Ni adatoms and trimers on graphene. First-principles calculations combined with symmetry considerations explain our experimental results by an orbitally controlled interaction of the adatoms and clusters with the Dirac electrons in graphene.