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

TL;DR

This paper investigates how superconducting and ferromagnetic interactions influence charge transport in junctions, emphasizing the role of spin-active scattering and analyzing different geometries including quantum point contacts and quantum dots.

Contribution

It demonstrates that spin-active scattering is crucial for understanding charge transport in quantum point contacts and even-state quantum dots, providing explanations for experimental observations.

Findings

Spin-active scattering is essential in quantum point contacts.

Kondo peak splitting can be used for spin filtering.

Spin-active scattering explains mini-gap features in quantum dots.

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 hybridisations 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.