Kondo effect of an adatom in graphene and its scanning tunneling spectroscopy

TL;DR

This paper investigates the Kondo effect of a magnetic adatom on graphene, revealing how graphene's unique properties influence the Kondo resonance, its spectroscopic signatures, and the impact of tunneling channels, providing insights for experimental exploration.

Contribution

It demonstrates that graphene's linear dispersion facilitates Kondo resonance formation over a wider parameter range and analyzes the spectral features and tunneling effects in detail.

Findings

Kondo resonance can form across various regimes in graphene.

Spectral lineshapes vary from sharp peaks to Fano-like features.

STM spectra show particle-hole asymmetry influenced by gate voltages.

Abstract

We study the Kondo effect of a single magnetic adatom on the surface of graphene. It was shown that the unique linear dispersion relation near the Dirac points in graphene makes it more easy to form the local magnetic moment, which simply means that the Kondo resonance can be observed in a more wider parameter region than in the metallic host. The result indicates that the Kondo resonance indeed can form ranged from the Kondo regime, to the mixed valence, even to the empty orbital regime. While the Kondo resonance displays as a sharp peak in the first regime, it has a peak-dip structure and/or an anti-resonance in the remaining two regimes, which result from the Fano resonance due to the significant background leaded by dramatically broadening of the impurity level in graphene. We also study the scanning tunneling microscopy (STM) spectra of the adatom and they show obvious particle-hole asymmetry when the chemical potential is tuned by the gate voltages applied to the graphene. Finally, we explore the influence of the direct tunneling channel between the STM tip and the graphene on the Kondo resonance and find that the lineshape of the Kondo resonance is unaffected, which can be attributed to unusual large asymmetry factor in graphene. Our study indicates that the graphene is an ideal platform to study systematically the Kondo physics and these results are useful to further stimulate the relevant experimental studies on the system.