Mechanism of generation of a Josephson phase shift by an Abrikosov vortex

TL;DR

This study uncovers how Abrikosov vortices induce long-range Josephson phase shifts through magnetic fields outside electrodes and circulating currents inside, revealing two distinct mechanisms with implications for electronic device development.

Contribution

The paper identifies and distinguishes two mechanisms of vortex-induced Josephson phase shifts, combining experimental, theoretical, and numerical analysis.

Findings

Vortex-induced phase shift is terminated by the junction, not beyond it.

A crossover from linear to superlinear phase shift dependence occurs near the penetration depth.

Two mechanisms are identified: one from circulating currents inside superconductors, another from stray magnetic fields outside.

Abstract

Abrikosov vortex contains magnetic field and circulating currents that decay at a short range $\lambda \sim 100$ nm. However, the vortex can induce a long range Josephson phase shift at distances $r\sim\mu$m$\gg\lambda$. The mechanism of this puzzling phenomenon is not clearly understood. Here we present a systematic study of vortex-induced phase shift in planar Josephson junctions. We make two key observations: (i) The cutoff effect: although vortex-induce phase shift is a long-range phenomenon, it is terminated by the junction and does not persists beyond it. (ii) A crossover from linear to superlinear dependence of the phase shift on the vortex polar angle occurs upon approaching of the vortex to the junction. The crossover occurs at a distance comparable with the penetration depth. This, together with theoretical and numerical analysis of the problem, allows unambiguous identification of two distinct and independent mechanisms. The short range mechanism is due to circulating vortex currents {\it inside} superconducting electrodes without involvement of magnetic field. The long range mechanism is due to stray magnetic fields {\it outside} electrodes without circulating vortex currents. We argue that understanding of controlling parameters of vortex-induced Josephson phase shift can be used for development of compact and fast electronic devices with low dissipation power.