Phase diagram and dependence of the critical temperature Tc on the pressure for Tl0.5Pb0.5Sr2Ca1-xYxCu2O7

Using a mean-field BCS-like approach on the bidimensional extended Hubbard Hamiltonian we calculate the superconducting transition temperature T-c as a function of the hole content nh. This method can be used to determine the critical temperatures T-c either for the extended s-wave or d-wave symmetry. We can also describe the pressure effects on T-c by introducing the assumption that it induces a change in the magnitude V of the attractive potential. This assumption yields an explanation for the intrinsic term, and together with the well known change in nh, we set the critical temperature as T-c = T-c(n(h)(P), V(P)). Then, we obtain a general expansion of T-c in terms of the pressure P and the hole content nh. We apply this expansion to the Tl0.5Pb0.5Sr2Ca1-xYxCu2O7 system (0.0 less than or equal to x less than or equal to 0.35) and our results provide a good fitting for the experimental data for the variation of T-c with the pressure P and n(h). (C) 2001 Elsevier Science B.V. All rights reserved.