PHASE-DIAGRAM OF HIGH-T-C SUPERCONDUCTORS - INFLUENCE OF ANISOTROPY AND DISORDER

We propose a phase diagram for the vortex structure of high-temperatur e superconductors which incorporates the effects of anisotropy and dis order. It is based on numerical simulations using the three-dimensiona l Josephson-junction array model. We support the results with an estim ation of the internal energy and configurational entropy of the system . Our results give a unified picture of the behavior of the vortex lat tice, from the very anisotropic Bi2Sr2CaCu2O8 to the less anisotropic YBa2Cu3O7, and from the first-order melting ocurring in clean samples to the continuous transitions observed in samples with defects.