COEXISTENCE OF BAND JAHN-TELLER DISTORTION AND SUPERCONDUCTIVITY IN CORRELATED SYSTEMS

The coexistence of the band Jahn-Teller (BJT) effect with superconduct ivity (SC) is studied for correlated systems with orbitally degenerate bands using a simple model. The Hubbard model for a doubly degenerate orbital with the on-site intraorbital Coulomb repulsion created in th e slave boson formalism and the interorbital Coulomb repulsion treated in the Hartree-Fock mean field approximation, describes the correlate d system. The model further incorporates the BJT interaction and a pai ring term to account for the lattice distortion and superconductivity, respectively. It is found that structural distortion tends to suppres s superconductivity and when SC sets in at low temperatures, the growt h of the lattice distortion is arrested. The phase diagram comprising of the SC and structural transition temperatures T-c and T-s versus th e dopant concentration delta reveals that the highest obtainable T-c f or an optimum doping is limited by structural transition. The dependen ce of the occupation probabilities of the different bands as well as t he density of states in the distorted-superconducting phase, on electr on correlation has been discussed.