Compensation of the Kondo effect in quantum dots coupled to ferromagnetic leads within equation of motion approach

TL;DR

This paper introduces a new approximation within the equation of motion approach for spin-polarized transport in quantum dots with ferromagnetic leads, improving accuracy in spin polarization predictions and correctly capturing the Kondo effect.

Contribution

A novel approximation scheme within the EOM approach that better matches NRG results for spin polarization and accurately restores the Kondo effect in ferromagnetic quantum dot systems.

Findings

The new method yields spin polarization values closer to NRG.

It correctly restores the Kondo effect with unpolarized transport.

Both methods agree on the splitting of Kondo peaks due to ferromagnetism.

Abstract

We propose a new approximation scheme within equation of motion approach (EOM) to spin polarized transport through a quantum dot coupled to ferromagnetic leads. It has some advantages over a widely used in the literature standard EOM technique, in particular when we are interested in spin polarized quantities. Namely, it gives the values of the dot spin polarization which are closer to the ones obtained within numerical renormalization group (NRG), than the standard EOM approach. While restoring the Kondo effect, the spin polarization vanishes and the transport becomes unpolarized, in agreement with NRG and a real time diagrammatic calculations. The standard EOM procedure gives nonzero values of the spin polarization, and the transport is still spin polarized. Both approximations give the same correct splitting of the Kondo peaks due to ferromagnetism in the electrodes.