The electron–hole asymmetry in the cuprate superconductors

Abstract

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.