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

Abstract

The characteristics of the Shockley surface states on $\mathrm{Cu}(111)$ in the presence of $\mathrm{Co}$ 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 $\mathrm{Co}$ ``$d$'' orbitals with bulk and surface states are obtained. We show that $\mathrm{Co}$ $3d$ orbitals hybridize mostly with $\mathrm{Cu}$ 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 $\mathrm{Cu}$ bulk electrons.