MIXED PHASES IN U(N) SUPERCONDUCTIVITY

We consider a general class of type-II superconductors which are descr ibed by N complex order parameters (OP's), with an overall U(N) symmet ry far the energy functional. In the lowest-energy state, each OP adop ts its own particular lattice structure, making the spatial variation of the overall condensate very complex. We present detailed results fo r the case N=2. We also treat the limit N-->infinity, which allows us to resolve a recent controversy, by showing that all previous studies are fundamentally flawed. [S0163-1829(98)02426-6].