Simple model for scanning tunneling spectroscopy of noble metal surfaces with adsorbed Kondo impurities

TL;DR

This paper presents a simple, realistic model for interpreting scanning tunneling spectroscopy of noble metal surfaces with Kondo-impurity atoms, emphasizing the importance of surface potential and tunneling details.

Contribution

The model incorporates realistic surface potentials and orbital descriptions, providing insights into Fano lineshape variations in Kondo impurity spectroscopy.

Findings

Fano lineshapes are sensitive to adsorbate-surface interactions.

Closer adsorbate proximity increases lineshape asymmetry.

Application to Co on Cu explains surface-dependent lineshape differences.

Abstract

A simple model is introduced to describe conductance measurements between a scanning tunneling microscope (STM) tip and a noble metal surface with adsorbed transition metal atoms which display the Kondo effect. The model assumes a realistic parameterization of the potential created by the surface and a d3z2-r2 orbital for the description of the adsorbate. Fano lineshapes associated with the Kondo resonance are found to be sensitive to details of the adsorbate-substrate interaction. For instance, bringing the adsorbate closer to the surface leads to more asymmetric lineshapes while their dependence on the tip distance is weak. We find that it is important to use a realistic surface potential, to properly include the tunnelling matrix elements to the tip and to use substrate states which are orthogonal to the adsorbate and tip states. An application of our model to Co adsorbed on Cu explains the difference in the lineshapes observed between Cu(100) and Cu(111) surfaces.