Zurek-Kibble Mechanism for the Spontaneous Vortex Formation in $Nb-Al/Al_{ox}/Nb$ Josephson Tunnel Junctions: New Theory and Experiment

摘要

New scaling behavior has been both predicted and observed in the spontaneousproduction of fluxons in quenched $Nb-Al/Al_{ox}/Nb$ annular Josephson tunneljunctions as a function of the quench time, $\tau_{Q}$. The probability $f_{1}$to trap a single defect during the N-S phase transition clearly follows anallometric dependence on $\tau_{Q}$ with a scaling exponent $\sigma = 0.5$, aspredicted from the Zurek-Kibble mechanism for {\it realistic} JTJs formed bystrongly coupled superconductors. This definitive experiment replaces onereported by us earlier, in which an idealised model was used that predicted$\sigma = 0.25$, commensurate with the then much poorer data. Our experimentremains the only condensed matter experiment to date to have measured a scalingexponent with any reliability.