CHARGE FLUCTUATION IN THE D-P MODEL - EFFECTS OF THE REPULSIVE INTERACTION BETWEEN D-HOLES AND P-HOLES

We investigate effects of the repulsive interaction U(pd) between holes on the nearest-neighbor Cu- and O-sites in the d-p model, a model suitable to describe the CuO2 plane in high-temperature superconductors. It is found that the condition for a metal-insulator (M-I) transition to occur at the half-filled case is modified. Furthermore, the charge susceptibility is found to be enhanced by U(pd), except for the region around the critical point of the M-I transition; it indeed diverges at a certain value of U(pd). Possible relevance of the enhanced charge susceptibility to the mechanism of the high T(c) superconductivity is discussed.