Critical Fluctuations and Disorder at the Vortex Liquid to Crystal Transition in Type-II Superconductors

We present a functional renormalization group (FRG) analysis of a Landau-Ginzburg model of type-II superconductors (generalized to n/2 complex fields) in a magnetic field, for both a pure and a disordered system. The disordered system supports a stable FRG fixed point for 1<n<4, identical to that of the disordered O\(n\) model in d-2 dimensions. The pure system has a stable fixed point only for n>4 indicating a first order transition for n = 2. We speculate that the recent experimental findings that disorder removes the first order transition are consistent with these calculations.