Search for spontaneous nucleation of magnetic flux during rapid cooling ofYBa2Cu3O7-delta films through T-c

We describe an experimental search for spontaneous formation of flux lines during a rapid quench of thin YBa2Cu3O7-delta films through T-c. This effec t is expected according to the Kibble-Zurek mechanism of a creation of topo logical defects of the order parameter during a symmetry-breaking phase tra nsition. Spontaneously formed vortices were previously observed in superflu id He-3, while a similar experiment in superfluid He-4 gave negative result s. Using a high-T-c superconducting quantum interference device, we measure d both the magnetic flux in the sample during a quench with a sensitivity o f 20 phi(0)/cm(2), and the held noise which one would expect from flux line s pinned in the film. The sensitivity was sufficient to detect spontaneous flux ata level corresponding to 10(-3) of the prediction. Within our resolu tion, we saw no evidence for this effect. [S0163-1929(99)06533-9].