On Compound Vortices in a Two-Component Ginzburg-Landau Functional

We study the structure of vortex solutions in a Ginzburg-Landau system for two complex-valued order parameters. We consider the Dirichlet problem in the disk in R-2 with symmetric, degree-one boundary condition, as well as the associated degree-one entire solutions in all of R2. Each problem has degree-one equivariant solutions with radially symmetric profile vanishing at the origin, of the same form as the unique (complex scalar) Ginzburg-Landau minimizer. We find that there is a range of parameters for which these equivariant solutions are the unique locally energy-minimizing solutions for the coupled system. Surprisingly, there is also a parameter regime in which the equivariant solutions are unstable, and minimizers must vanish separately in each component of the order parameter.