Search for Spontaneous Nucleation of Magnetic Flux During Rapid Cooling of YBCO films Through Tc

TL;DR

This study experimentally searched for spontaneous magnetic flux formation in YBCO films during rapid cooling through Tc, testing the Kibble-Zurek mechanism, but found no evidence of such flux lines within their detection limits.

Contribution

The paper provides the first experimental test of spontaneous flux formation in high-Tc superconducting films during rapid quenching, with null results setting upper bounds on defect formation.

Findings

No evidence of spontaneous flux lines detected

Sensitivity was sufficient to detect flux at 10^(-3) of theoretical prediction

Results constrain the applicability of the Kibble-Zurek mechanism in this context

Abstract

We describe an experimental search for spontaneous formation of flux lines during a rapid quench of thin YBaCuO films through Tc. This effect is expected according to the Kibble-Zurek mechanism of a creation of topological defects of the order parameter during a symmetry breaking phase transition. Spontaneously formed vortices were previously observed in superfluid 3He, while a similar experiment in superfluid 4He gave negative results. Using a high Tc SQUID, we measured both the magnetic flux in the sample during a quench with a sensitivity of 20 phi-0/cm^2, and the field noise which one would expect from flux lines pinned in the film. The sensitivity was sufficient to detect spontaneous flux at a level corresponding to 10^(-3) of the prediction. Within our resolution, we saw no evidence for this effect.