Multiple 0 - pi transitions in SIFS Josephson tunnel junctions

TL;DR

This study experimentally investigates superconducting coupling in Nb/Al/Al2O3/Ni3Al/Nb Josephson junctions, revealing multiple 0-pi transitions and confirming theoretical predictions with high reproducibility and detailed multilayer fabrication.

Contribution

It introduces a new fabrication process for reproducible multilayer Josephson junctions and demonstrates multiple 0-pi transitions consistent with theoretical models.

Findings

Observed up to six damped oscillations of critical current density.

Identified three distinct 0-pi transitions in the ground state.

Found exponential decay length larger than oscillation period.

Abstract

We report on experimental studies of superconducting coupling through a thin Ni76Al24 film. A new patterning process has been developed, which allows in combination with the wedge shaped deposition technique the in situ deposition of 20 single Nb/Al/Al2O3/Ni3Al/Nb multilayers, each with its own well defined Ni3Al thickness. Every single multilayer consists of 10 different sized Josephson junctions, showing a high reproducibility and scaling with its junction area. Up to six damped oscillations of the critical current density against F-layer thickness were observed, revealing three single 0-pi transitions in the ground state of Josephson junctions. Contrary to former experimental studies, the exponential decay length is one magnitude larger than the oscillation period defining decay length. The theoretical predictions based on linearized Eilenberger equations result in excellent agreement of theory and experimental results.