Hybridization of impurity states with the Shockley surface band versus bulk states

The characteristics of the Shockley surface states on Cu(111) in the presence of Co impurity adsorbates are studied by means of one electron calculation performed using a well parametrized Hamiltonian in a local basis. Local densities of states in the spillover region as well as the relative hybridization strengths of Co “d” orbitals with bulk and surface states are obtained. We show that Co 3d orbitals hybridize mostly with Cu bulk conduction states, thus giving ground to recent experimental results [ N. Knorr, M. A. Schneider, L. Diekhoner, P. Wahl and K. Kern Phys. Rev. Lett. 88 096804 (2002)] in the sense that the observed Kondo resonances are being dominated by Cu bulk electrons.