The signature of subsurface Kondo impurities in the local tunnel current

TL;DR

This paper theoretically analyzes how subsurface Kondo impurities affect the local tunnel current in STM-like setups, revealing the significant role of multiple electron scattering and impurity position on conductance near the Kondo resonance.

Contribution

It introduces a model accounting for multiple scattering effects of subsurface Kondo impurities on tunnel conductance, highlighting the impact of impurity position and resonance.

Findings

Multiple scattering significantly influences conductance near the Kondo resonance.

The sign and shape of the Kondo anomaly depend on the impurity's position.

The model captures the conductance dependence on voltage and defect location.

Abstract

The conductance of a tunnel point-contact in an STM-like geometry having a single defect placed below the surface is investigated theoretically. The effect of multiple electron scattering by the defect after reflections by the metal surface is taken into account. In the approximation of s-wave scattering the dependence of the conductance on the applied voltage and the position of the defect is obtained. The results are illustrated for a model s-wave phase shift describing Kondo-resonance scattering. We demonstrate that multiple electron scattering by the magnetic impurity plays a decisive role in the point-contact conductance at voltages near the Kondo resonance. We find that the sign and shape of the Kondo anomaly depends on the position of the defect.