Nucleation, growth and kinetics of the vortex phase in thin superconducting strips

The kinetics of normal phase nucleation and flux line condensation in type-II superconductors are investigated by a numerical and analytical study of the time-dependent Ginzburg-Landau equation. It is shown that spontaneous nucleation and the consequent penetration of vortices into thin superconducting films, subjected to a magnetic field, can be considered as a nonlinear stage of primary instability of the current-carrying superconducting state. The development of the instability leads to the formation of a chain of vortices. In the presence of high transport current, the vortex phase nucleates in the superconducting strips in the form of macroscopic droplets having multiple topological charge. The stability and the dynamics of the droplets are discussed. It is found that pinning suppresses the droplet formation.