Cooper pair splitting in diffusive magnetic SQUIDs

TL;DR

This paper investigates Josephson junctions with disordered magnetic weak links, revealing mesoscopic fluctuations, Cooper pair splitting effects, and a $2 ext{ extPhi}_0$ periodicity in the supercurrent.

Contribution

It introduces a detailed analysis of Cooper pair splitting and flux dependence in magnetic SQUIDs with disordered arms, highlighting the role of mesoscopic fluctuations and $ ext{ extPhi}_0$ junction behavior.

Findings

Mesoscopic fluctuations dominate the Josephson effect in long disordered magnetic links.

Cooper pair splitting causes a $2 ext{ extPhi}_0$ periodicity in the supercurrent.

The system exhibits a $ ext{ extPhi}_0$ junction with sample-dependent phase shifts.

Abstract

We study Josephson junctions with weak links consisting of two parallel disordered arms with magnetic properties -- ferromagnetic, half-metallic or normal with magnetic impurities. In the case of long links, the Josephson effect is dominated by mesoscopic fluctuations. In this regime, the system realises a $\varphi_0$ junction with sample-dependent $\varphi_0$ and critical current. Cooper pair splitting between the two arms plays a major role and leads to $2\Phi_0$ periodicity of the current as a function of flux between the arms. We calculate the current and its flux and polarization dependence for the three types of magnetic links.