Evidence for triplet superconductivity in Josephson junctions with ferromagnetic Cu$_{2}$MnAl-Heusler barriers

TL;DR

This study demonstrates evidence of triplet superconductivity in Josephson junctions with Cu$_2$MnAl barriers, showing how annealing induces ferromagnetic order and enhances the critical current, indicating a triplet pairing component.

Contribution

The paper provides experimental evidence for triplet superconductivity in ferromagnetic Heusler alloy barriers within Josephson junctions, highlighting the role of annealing in inducing ferromagnetic order.

Findings

Critical current density decreases exponentially with barrier thickness in the non-ferromagnetic state.

Annealing induces ferromagnetic order and enhances the critical current.

Presence of a triplet component in the superconducting pairing function.

Abstract

We have studied Josephson junctions with barriers prepared from the Heusler compound Cu$_2$MnAl. In the as-prepared state the Cu$_2$MnAl layers are non ferromagnetic and the critical Josephson current density $j_{c}$ decreases exponentially with the thickness of the Heusler layers $d_{F}$. On annealing the junctions at 240\degree C the Heusler layers develop ferromagnetic order and we observe a dependence $j_{c}(d_{F}$) with $j_{c}$ strongly enhanced and weakly thickness dependent in the thickness range 7.0 nm < $d_{F}$ < 10.6 nm. We attribute this feature to a triplet component in the superconducting pairing function generated by the specific magnetization profile inside thin Cu$_2$MnAl layers.