Kondo effect and spin-active scattering in ferromagnet-superconductor junctions

Abstract

We study the interplay of superconducting and ferromagnetic correlations on charge transport in different geometries with a focus on both a quantum point contact as well as a quantum dot in the even and the odd state with and without spin-active scattering at the interface. In order to obtain a complete picture of the charge transport we calculate the full counting statistics in all cases and compare the results with experimental data. We show that spin-active scattering is an essential ingredient in the description of quantum point contacts. This holds also for quantum dots in an even charge state, whereas it is strongly suppressed in a typical Kondo situation. We explain this feature by the strong asymmetry of the hybridizations with the quantum dot and show how Kondo peak splitting in a magnetic field can be used for spin filtering. For the quantum dot in the even state, spin-active scattering allows for an explanation of the experimentally observed mini-gap feature.