The electron-hole asymmetry in the cuprate superconductors

We investigate the electron-hole asymmetry in the superconduting state based on the ingap state and the superexchange interaction Js in the d-p model, where we take the antiferromagnetic fluctuations in the fluctuation-exchange approximation and take the superconducting fluctuations in the self-consistent t-matrix approximation. We show that the superconducting gap in the hole-doped region is several times larger than that in the electron-doped region. This difference is due to the intrinsic nature of the ingap states which are intimately related with the Zhang-Rice singlets in the hole-doped systems and are correlated d-electrons in the electron-doped systems, respectively