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

We propose a new approximation scheme within the equation of motion approach (EOM) to spin polarized transport through a quantum dot coupled to ferromagnetic leads. It has some advantages over a standard EOM technique widely used in the literature, in particular when we are interested in spin polarized quantities. Namely, it gives values of the dot spin polarization which are closer to the ones obtained within the 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 real time diagrammatic calculations. The standard EOM procedure gives non-zero 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