▎ 摘　　要

In the limit of low adatom concentration, we obtain exact analytic expressions for the local and total density of states (LDOS, TDOS) for a tight-binding model of adatoms on graphene. The model is not limited to nearest-neighbor hopping but can include hopping between carbon atoms at any separation. We also find an analytical expression for the spectral function A(k, E) of an electron of Bloch vector k and energy E on the graphene lattice, to first order in the adatom concentration. We treat the electron-electron interaction by including a Hubbard term on the adatom, which we solve within a mean-field approximation. For finite Hubbard U, we find the spin-polarized LDOS, TDOS, and spectral function self-consistently. For any choice of parameters of the tight-binding model within mean-field theory, we find a critical value of U above which a moment develops on the adatom. Preliminary calculations also indicate that this moment can be switched on and off by varying the Fermi energy. For most choices of parameters, we find a substantial charge transfer from the adatom to the graphene host.