Conductance and Kondo Effect in a Controlled Single-Atom Contact

Abstract

The tip of a low-temperature scanning tunneling microscope is brought into contact with individual cobalt atoms adsorbed on Cu(100). A smooth transition from the tunneling regime to contact occurs at a conductance of $G\approx G_0$. Spectroscopy in the contact regime, i.e., at currents in a $\mu \mathrm{A}$ range, was achieved and indicated a significant change of the Kondo temperature $T_K$. Calculations indicate that the proximity of the tip shifts the cobalt $d$ band and thus affects $T_K$.