Spontaneous Fluxon Production in Annular Josephson Tunnel Junctions in the Presence of a Magnetic Field

TL;DR

This paper investigates how magnetic fields influence spontaneous fluxon creation in annular Josephson junctions during thermal quenches, aligning experimental results with the Kibble-Zurek defect formation theory.

Contribution

It demonstrates the dependence of fluxon trapping probability on magnetic field strength and sample size, providing experimental validation of the Kibble-Zurek mechanism in this context.

Findings

Fluxon trapping probability varies with magnetic field intensity.

Sample circumference significantly affects defect formation.

Results support the causal bounds predicted by the Kibble-Zurek theory.

Abstract

We report on the spontaneous production of fluxons in the presence of a symmetry-breaking magnetic field for annular Josephson tunnel junctions during a thermal quench. The dependence on field intensity $B$ of the probability $\bar{f_1}$ to trap a single defect during the N-S phase transition drastically depends on the sample circumferences. We show that the data can be understood in the framework of the Kibble-Zurek picture of spontaneous defect formation controlled by causal bounds.