Kondo physics of magnetic adatoms on metallic surfaces when the onset of the surface conduction density of states crosses the Fermi level

TL;DR

This paper investigates how the proximity of surface conduction states to the Fermi level influences the Kondo effect in magnetic adatoms on metallic surfaces, revealing significant modifications in thermodynamic, spectral, and conductance properties.

Contribution

It introduces a detailed analysis of the impact of Shockley surface state onset on Kondo physics using NRG, highlighting non-trivial effects near the Fermi level not previously characterized.

Findings

Impurity susceptibility and entropy show negative values and logarithmic decay.

Spectral density at the Fermi level is suppressed near $D_s \\sim E_F$.

Conductance through the impurity is reduced by approximately 25%.

Abstract

We study the role of the onset of Shockley states, $D_s$, belonging to (111) surfaces of Cu, Ag and Au in the Kondo effect when a magnetic impurity is deposited on them. When $D_s$ approaches to the Fermi level, $E_F$, thing that can be done by compressing (stretching) the metallic sample, we found that most of the thermodynamic and dynamic properties of the impurity are affected in a non trivial way. We model the system by a generic Anderson impurity model and solve it by using the numerical renormalization group, NRG, technique. In particular, the impurity contribution to magnetic susceptibility and entropy as a function of temperature exhibit negative values and goes to zero slowly in a logarithmic shape. Furthermore, we found a suppression of the spectral density weight at the Fermi level when $D_s\sim E_F$ even in the Kondo regime. As a consequence, the conductance through the impurity is strongly reduced by near $25\%$ of the unitary value $2e^2/h$. Finally, we analyze these features in realistic systems like Co on Ag(111) reported in the literature.