Spin resolved Andreev reflection in ferromagnet-superconductor junctions with Zeeman splitting

TL;DR

This paper investigates spin-resolved Andreev reflection in ferromagnet-superconductor junctions under strong Zeeman splitting, revealing how spin channels behave differently with voltage and polarization.

Contribution

It introduces a theoretical framework for spin-resolved Andreev reflection considering dominant Zeeman effects, highlighting novel behaviors in conductance asymmetry and transition dynamics.

Findings

Spin-up and spin-down Andreev reflections are resolved at higher voltages.

Conductance becomes asymmetric with voltage reversal.

Transition from Andreev to tunnel conductance shows non-trivial dependence on spin polarization.

Abstract

Andreev reflection in ferromagnet-superconductor junctions is derived in a regime in which Zeeman splitting dominates the response of the superconductor to an applied magnetic field. Spin-up and spin-down Andreev reflections are shown to be resolved as voltage is increased. In the metallic limit, the transition from Andreev to tunnel conductivity in the spin-up channels has a non trivial behavior when spin polarization is increased. The conductance is asymmetric in a voltage reversal.