SUPERCONDUCTING PHASES OF THE EXTENDED HUBBARD-MODEL FOR DOPED SYSTEMS

Using an extended Hubbard model with interactions and hopping terms be tween sites situated farther than nearest neighbouring ones, applying the Hartree-Fock-Gor'kov decoupling scheme and considering the exact q uaziparticle density of states a systematic investigation of pairing s tates with different symmetry has been carried out in order to constru ct superconducting phase diagrams of the model. Having determined all the possible superconducting pairing states self-consistently for a fi xed set of model parameters, such as interaction values, band filling and temperature, the stable state is chosen on the basis of a rigorous free-energy analysis. The structure of phase diagram and the stabilit y of different symmetry pairing states show strong dependency on model parameters.