According to a prediction by Kibble and Zurek, magnetic flux lines are spontaneously created during a conductor-superconductor phase transition under nonequilibrium conditions.  This model is relevant both to cosmology and to nonequilibrium thermodynamics. The model predicts the dependence of the vortex density on cooling rate and the exponential decay in the correlation function.

In order to test this model we developed a new magneto-optical system with single flux resolution. Kerr effect in thin EuSe film is used to measure locally magnetic field above the surface of superconductor. The sample (thin film of niobium) heated above critical temperature by 10 ns laser pulse, and then the heat transferred from the film to the sapphire substrate. In this setup cooling rates are in the order of magnitude of 10⁹ K/sec.

The density of spontaneously emerged vortices depends on the cooling rate in a way consistent with the theoretical prediction. On the other hand, the correlations between spontaneously created vortices show an unexpected long range behavior.