CHARGE FLUCTUATION AND SUPERCONDUCTIVITY IN THE ONE-DIMENSIONAL D-P MODEL

The one-dimensional two-band Hubbard model, simulating a Cu-O linear chain with infinite intra-site Coulomb repulsion among holes at the Cu-sites, is solved exactly by using the numerical diagonalization method. It is confirmed that inter-site Coulomb repulsion between holes at the nearest-neighbor Cu- and 0-sites enhances the charge fluctuation as well as the superconducting fluctuations, and when it exceeds a certain critical value the system becomes unstable towards the phase separation. By assuming the Luttinger liquid relations to hold in the present system, the critical exponents in the superconducting, CDW and SDW correlation functions are also calculated. The results suggest that in the proximity of the phase boundary towards the phase separation, the superconducting correlation is dominant compared with the CDW and SDW correlations.