Charge Fluctuation and Superconductivity in the d-p Model

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We investigate effects of the repulsive interaction U.. between ltoles on the nearest-neighbor Cu- auad O-sites in the d-p model with infinite repulsion on the Cu site usiuagtlae auxiliary boson techutique and the l / N expansion naethod. It is found that tlte con-dition for a metal-insulator (M-I) transition to occur at the half-filled case ismodified. We then investigate the charge susceptibility; it is found that the ther-modynamic charge susceptibility is enhanced by U., except for the region arotund thecritical point of tlae M-I transitioua. It is found to diverge at a certain value of U,.,which implies 811 instability toward a phase separatiouv. On tlae basis of tlaese calcula-tions, we obtain plvase diagrams, whicla consist of the metallic, uxastable (phase-separating) and iuasulating phases. Furthermore, NVC calculate the quasiparticle iuaterac-Lion and fiutd that tlte charge fluctuation induces attractive interaction comparable inmagnitude to the repulsive iu?teraction origim?ating from tlae on-site repulsiona U. inboth of the .5- and #-wave channel; in the immediate vicinity of the instability, theattraction can overcome the repulsion.
社団法人日本物理学会の論文
1992-02-15