Kondo Effect of Co Adatoms on Ag Monolayers on Noble Metal Surfaces

The Kondo temperature TK of single Co adatoms on monolayers of Ag on Cu and Au(111) is determined using Scanning Tunneling Spectroscopy. TK of Co on a single monolayer of Ag on either substrate is essentially the same as that of Co on a homogenous Ag(111) crystal. Besides giving strong evidence that the interaction of surface Kondo impurities with the substrate is very local in nature the data show that the energy scale of the many-electron Kondo state is insensitive to the properties of surface states and to the energetic position of the projected bulk band edges. We demonstrate that the trend of the Kondo temperature of Co adatoms is correlated to the impurity's d-band shift as obtained from the Hammer and Nørskovs model of reactivity neglecting many-body effects.