  This paper is devoted to an analysis of vortex-nucleation for a
Ginzburg-Landau functional with discontinuous constraint. This functional has
been proposed as a model for vortex-pinning, and usually accounts for the
energy resulting from the interface of two superconductors. The critical
applied magnetic field for vortex nucleation is estimated in the London
singular limit, and as a by-product, results concerning vortex-pinning and
boundary conditions on the interface are obtained.
