Kondo effect in single atom contacts: the importance of the atomic geometry

TL;DR

This study investigates the Kondo effect in single cobalt atom junctions on copper surfaces, revealing how atomic geometry influences the Kondo temperature and electronic properties at the nanoscale.

Contribution

It provides new insights into how atomic geometry affects the Kondo effect in single-atom contacts, combining experimental measurements with ab-initio calculations.

Findings

Kondo temperature remains constant across tip-sample distances on Cu(111).

Different behavior observed on Cu(100) due to structural relaxations.

Electronic properties are strongly influenced by atomic geometry at the contact point.

Abstract

Co single atom junctions on copper surfaces are studied by scanning tunneling microscopy and ab-initio calculations. The Kondo temperature of single cobalt atoms on the Cu(111) surface has been measured at various tip-sample distances ranging from tunneling to the point contact regime. The experiments show a constant Kondo temperature for a whole range of tip-substrate distances consistently with the predicted energy position of the spin-polarized d-levels of Co. This is in striking difference to experiments on Co/Cu(100) junctions, where a substantial increase of the Kondo temperature has been found. Our calculations reveal that the different behavior of the Co adatoms on the two Cu surfaces originates from the interplay between the structural relaxations and the electronic properties in the near-contact regime.