Kondo resonance of a Co atom exchange coupled to a ferromagnetic tip

TL;DR

This study investigates the Kondo effect of a cobalt atom on copper using low-temperature scanning tunneling microscopy, revealing a spin-split asymmetric resonance influenced by exchange coupling with a ferromagnetic tip.

Contribution

It provides a detailed experimental and theoretical analysis of the Kondo resonance in a Co atom junction with a ferromagnetic tip, highlighting the effects of exchange coupling and spin polarization.

Findings

Observation of spin-split asymmetric Kondo resonance

Ab initio calculations show exchange coupling is sufficient to cause splitting

Quantitative analysis indicates weak junction spin polarization

Abstract

The Kondo effect of a Co atom on Cu(100) was investigated with a low-temperature scanning tunneling microscope using a monoatomically sharp nickel tip. Upon a tip-Co contact, the differential conductance spectra exhibit a spin-split asymmetric Kondo resonance. The computed ab initio value of the exchange coupling is too small to suppress the Kondo effect, but sufficiently large to produce the splitting observed. A quantitative analysis of the line shape using the numerical renormalization group technique indicates that the junction spin polarization is weak.