Linear CoCu_nCo clusters on Cu(111) are fabricated by means of atomic manipulation. They represent a two-site Kondo system with tunable interaction. Scanning tunneling spectroscopy reveals oscillations of the Kondo temperature T_K with the number n of Cu atoms for n>=3. Density functional calculations show that the Ruderman-Kittel-Kasuya-Yosida interaction mediated by the Cu chains causes the oscillations. Calculations find ferromagnetic and antiferromagnetic interaction for n=1 and 2, respectively. Both interactions lead to a decrease of T_K as experimentally observed.
@article{arxiv.1105.3301,
title = {Two-Site Kondo Effect in Atomic Chains},
author = {N. Néel and R. Berndt and J. Kröger and T. O. Wehling and A. I. Lichtenstein and M. I. Katsnelson},
journal= {arXiv preprint arXiv:1105.3301},
year = {2015}
}