Conductance and Kondo effect of a controlled single atom contact

TL;DR

This study investigates the conductance and Kondo effect of a single cobalt atom contact using a low-temperature STM, revealing a transition from tunneling to contact and a change in Kondo temperature due to tip proximity.

Contribution

It demonstrates controlled contact formation with single atoms and shows how tip proximity influences the Kondo temperature and spectral line shape.

Findings

Transition from tunneling to contact with conductance ~ G0

Modified Kondo line shape at contact

Tip proximity shifts cobalt d-band and affects T_K

Abstract

The tip of a low-temperature scanning tunneling microscope is brought into contact with individual Kondo impurities (cobalt atoms) adsorbed on a Cu(100) surface. A smooth transition from the tunneling regime to a point contact with a conductance of $G\approx\text{G}_0$ occurs. Spectroscopy in the contact regime, {\it i. e.}, at currents in a $\mu\text{A}$ range was achieved. A modified line shape is observed indicating a significant change of the Kondo temperature $T_{\text{K}}$ at contact. Model calculations indicate that the proximity of the tip shifts the cobalt $d$-band and thus affects $T_{\text{K}}$.