| Graphene, a single layer of hexagonally bonded carbon atoms, is often hailed as a wonder material due to its remarkable intrinsic properties. It is the thinnest, the strongest, and the most stretchable crystal ever measured. Of all materials, it also exhibits the highest electron mobility and current density at room temperature. One potential application of graphene is for use in spintronic devices. However, external methods are required to induce magnetism on graphene, since pristine graphene is nonmagnetic. One proposal is to adsorb transition metal atoms to provide localized magnetic moments in graphene. Single Co atoms on graphene, in particular, have been extensively studied both theoretically and experimentally. Previous calculations, however, show significantly varying results on the bonding nature of Co/graphene system and none of the calculations is fully consistent with the experimental results. We investigate the stability and electronic properties of single Co atoms on graphene with near-exact auxiliary-field quantum Monte Carlo. Our findings are consistent with and provide an explanation for experimental results with Co on free-standing graphene. |
