Pseudogap due to antiferromagnetic fluctuations and the phase diagram of high-temperature oxide superconductors

A reduction of the density of states near the Fermi energy in the normal st ate (pseudogap) of high-temperature oxide superconductors is examined on th e basis of the two-dimensional tight-binding model with effective interacti ons due to antiferromagnetic fluctuations. By using antiferromagnetic corre lation lengths which are phenomenologically assumed, the doping dependence of the pseudogap is obtained. The superconducting transition temperature de creases and eventually vanishes due to the pseudogap as the hole concentrat ion is reduced.