Kondo effect of a Co atom on Cu(111) in contact with an Fe tip

TL;DR

This study investigates how the Kondo effect of a Co atom on Cu(111) is influenced by different metallic tips in a low-temperature scanning tunneling microscope, revealing tip-dependent modifications of the Kondo resonance.

Contribution

It provides new insights into how different tip materials affect the Kondo resonance of a single Co atom in STM experiments.

Findings

Fe tips broaden the Kondo resonance significantly.

Cu-covered W tips do not change the resonance width.

The changes are linked to hybridization affecting Co d state occupation.

Abstract

Single Co atoms, which exhibit a Kondo effect on Cu(111), are contacted with Cu and Fe tips in a low-temperature scanning tunneling microscope. With Fe tips, the Kondo effect persists with the Abrikosov-Suhl resonance significantly broadened. In contrast, for Cu-covered W tips, the resonance width remains almost constant throughout the tunneling and contact ranges. The distinct changes of the line width are interpreted in terms of modifications of the Co d state occupation owing to hybridization with the tip apex atoms.