ANALYSIS OF THE SHIFT IN THE SUPERCONDUCTING TRANSITION UNDER PRESSURE IN THE ANDERSON-HUBBARD 2-ORBITAL MODEL

The two-orbital Hubbard model is used to obtain formulas for the fermi on excitation spectrum in the energy bands hybridized by Anderson's in teraction. A transition to the Hubbard operators, which diagonalizes t he one-site part of the Hamiltonian, allows us to use the Green's temp erature function technique to take into account the interstitial jump term while studying the superconducting properties of the model. An an alysis of the lower part of the energy spectrum leads to a formula for the superconducting transition temperature T-c associated with the pa iring of quasiparticles in one of the correlated bands. The dependence of T-c on electron concentration and energy parameters determining th e intraatomic correlation is studied. Proposing a simple relation betw een the value of pressure (P) and width of the correlated band, the de pendence of T-c on the pressure was defined. Good agreement between th e theoretical calculation of the dependence of T-c on the pressure and the experimental results for Y1-xPrxBa2Cu3O7-delta is found. Comparis on of the theoretical and experimental results for the dependence of T -c and its derivative d(ln T-c)/dP on Sr and Bi-content (x) in La2-xSr xCuO4 has been made. It is concluded that the model under consideratio n can be used for the description of the shift in T-c under pressure f or a number of superconductors. (C) 1998 American Institute of Physics . [S1063-777X(98)00203-5].