Engineering quantum anomalous/valley Hall states in graphene via metal-atom adsorption: An ab-initio study

We systematically investigate the magnetic and electronic properties of graphene adsorbed with diluted 3d transition and noble-metal atoms using first-principles calculation methods. We find that most transition-metal atoms (i.e., Sc, Ti, V, Mn, Fe) favor the hollow adsorption site, and the interaction between magnetic adatoms and the pi orbital of graphene induces sizable exchange-field and Rashba spin-orbit coupling, which together open a nontrivial bulk gap near the Dirac K/K'(Gamma) points in the 4 x 4 (3 x 3) supercell of graphene leading to the quantum anomalous Hall effect. We also find that the noble-metal atoms (i.e., Cu, Ag, Au) prefer the top adsorption site, and the dominant inequality of the AB sublattice potential opens another kind of nontrivial bulk gap exhibiting the quantum-valley Hall effect in the 4 x 4 supercell of graphene.