A pertubative approach to the Kondo effect in magnetic atoms on nonmagnetic substrates

TL;DR

This paper develops a third-order perturbative method to accurately describe the Kondo effect and spin-flip inelastic tunneling in magnetic atoms on nonmagnetic substrates, aligning well with experimental conductance spectra.

Contribution

It introduces a third-order analytic expression for electron-spin self-energy enabling efficient and accurate modeling of complex electron transport phenomena.

Findings

Successfully models Kondo resonances and inelastic tunneling

Achieves quantitative agreement with experimental data

Lower computational cost compared to existing methods

Abstract

Recent experimental advances in scanning tunneling microscopy make the measurement of the conductance spectra of isolated and magnetically coupled atoms on nonmagnetic substrates possible. Notably these spectra are characterized by a competition between the Kondo effect and spin-flip inelastic electron tunneling. In particular they include Kondo resonances and a logarithmic enhancement of the conductance at voltages corresponding to magnetic excitations, two features that cannot be captured by second order perturbation theory in the electron-spin coupling. We have now derived a third order analytic expression for the electron-spin self-energy, which can be readily used in combination with the non-equilibrium Green's function scheme for electron transport at finite bias. We demonstrate that our method is capable of quantitative description the competition between Kondo resonances and spin-flip inelastic electron tunneling at a computational cost significantly lower than that of other approaches. The examples of Co and Fe on CuN are discussed in detail.