Statistical mechanics of flux lines in oxide superconductors

Abstract

The structure of the unpinned vortex liquid in strongly anisotropic layered high-T_c oxide superconductors in a magnetic field B perpendicular to the layer plane is investigated by using appropriate classical liquid-state theories. The direct correlation function so obtained is used as input for a parameter-free, first-principles calculation of the liquid-to-Abrikosov-lattice transition boundary T_f(B) within the framework of the density functional formalism. This transition boundary is found to have a shape and location similar to that observed in experiments on strongly anisotropic materials, e.g. Bi---Sr---Ca---Cu---O. The effects of random pinning disorder on the equilibrium density correlations of the vortex liquid and its freezing transition are investigated by combining the methods mentioned above with the replica formalism.