A low-temperature scanning tunneling microscope was employed to study the differential conductance in an atomic junction formed by an adsorbed Co atom on a Cu(100) surface and a copper-covered tip. A zero-bias anomaly (ZBA) reveals spin scattering off the Co atom, which is assigned to a Kondo effect. The ZBA exhibits a characteristic asymmetric lineshape when electrons tunnel between tip and sample, while upon the tip-Co contact it symmetrizes and broadens. Through density functional theory calculations and the non-equilibrium non-crossing approximation we show that the lineshape broadening is mainly a consequence of the additional coupling to the tip, while non-equilibrium effects only modify the large-bias tails of the ZBA.
@article{arxiv.1609.08955,
title = {From tunneling to contact in a magnetic atom: the non-equilibrium Kondo effect},
author = {Deung-Jang Choi and Paula Abufager and Laurent Limot and Nicolas Lorente},
journal= {arXiv preprint arXiv:1609.08955},
year = {2018}
}