Incomplete Andreev reflection in a clean Superconductor/Ferromagnet/Superconductor junction

TL;DR

This paper investigates the Josephson effect in a clean superconductor-ferromagnet-superconductor junction, revealing incomplete Andreev reflection and oscillatory critical current behavior influenced by exchange energy and temperature.

Contribution

It demonstrates the incomplete Andreev reflection in clean ferromagnet-superconductor interfaces and its impact on Josephson current oscillations, deviating from quasiclassical predictions.

Findings

Critical current oscillates with exchange energy and ferromagnet length.

Andreev channels with large incidence angles are suppressed at high exchange energy.

Temperature dependence of critical current differs from quasiclassical theory.

Abstract

We study the Josephson effect in a clean Superconductor-Ferromagnet-Superconductor junction for arbitrarily large spin polarizations. The Andreev reflection at a clean Ferromagnet-Superconductor interface is incomplete, and Andreev channels with a large incidence angle are progressively suppressed with increasing exchange energy. As a result, the critical current exhibits oscillations as a function of the exchange energy and of the length of the ferromagnet and has a temperature dependence which deviates from the one predicted by the quasiclassical theory.