Revealing Josephson vortex dynamics in proximity junctions below critical current

TL;DR

This study investigates the dynamics of Josephson vortices in Nb-Cu-Nb proximity junctions, revealing multiple regimes of vortex motion and identifying a fast hysteretic regime suitable for low-dissipative logic applications.

Contribution

It provides the first combined experimental and numerical analysis of Josephson vortex dynamics in proximity junctions, highlighting a novel hysteretic vortex entry/escape regime.

Findings

Multiple dynamic regimes of Josephson vortex motion identified.

Existence of a fast hysteretic vortex entry/escape regime.

Potential application in low-dissipative logic and memory devices.

Abstract

Made of a thin non-superconducting metal (N) sandwiched by two superconductors (S), SNS Josephson junctions enable novel quantum functionalities by mixing up the intrinsic electronic properties of N with the superconducting correlations induced from S by proximity. Electronic properties of these devices are governed by Andreev quasiparticles [1] which are absent in conventional SIS junctions whose insulating barrier (I) between the two S electrodes owns no electronic states. Here we focus on the Josephson vortex (JV) motion inside Nb-Cu-Nb proximity junctions subject to electric currents and magnetic fields. The results of local (Magnetic Force Microscopy) and global (transport) experiments provided simultaneously are compared with our numerical model, revealing the existence of several distinct dynamic regimes of the JV motion. One of them, identified as a fast hysteretic entry/escape below the critical value of Josephson current, is analyzed and suggested for low-dissipative logic and memory elements.