Comment on "Fano Resonance for Anderson Impurity Systems"

TL;DR

This paper critiques a recent analysis claiming a second Fano resonance in Kondo systems, arguing that the interpretation is conceptually flawed and undermines the validity of the previous spectral fits.

Contribution

It clarifies the conceptual misunderstanding in the previous work, emphasizing that the Kondo resonance does not produce a second Fano line shape.

Findings

The previous interpretation of the Fano resonance is conceptually incorrect.

The spectral fits based on that interpretation are not meaningful.

The analysis clarifies the nature of Fano interference in Kondo systems.

Abstract

In a recent Letter, Luo et al. (Phys. Rev. Lett. 92, 256602 (2004)) analyze the Fano line shapes obtained from scanning tunneling spectroscopy (STS) of transition metal impurities on a simple metal surface, in particular of the Ti/Au(111) and Ti/Ag(100) systems. As the key point of their analysis, they claim that there is not only a Fano interference effect between the impurity d-orbital and the conduction electron continuum, as derived in Ujsaghy et al. (Phys. Rev. Lett. 85, 2557 (2000)), but that the Kondo resonance in the d-electron spectral density has by itself a second Fano line shape, leading to the experimentally observed spectra. In the present note we point out that this analysis is conceptually incorrect. Therefore, the quantitative agreement of the fitted theoretical spectra with the experimental results is meaningless.