Mixed electronic states of high Tc cuprates superconductors

A model of high Tc cuprates superconductivity is proposed from the point of view that the electronic state of copper oxides can be described by the fermions constructed with newly defined operators. These operators are composed of d hole in Cu site and p hole in O site, and are identified as two types of free fermions. The electronic states are investigated in two cases of nearly non-doped region and the neighborhood of optimally doped region. The interplay between the superconducting and the pseudogap state can be explained by the mixed electronic state which composes of the BCS state and the local antiferromagnetic coupling state. The gap energy and the critical temperature of these states are estimated as a function of the doping quantity, respectively. It is found that Cooper pair formation in high Tc cuprates superconductors depends on the wave-function overlap of Cu and O holes.