Strong-Coupling Superconductivity in the Cuprate Oxide

Abstract

Superconductivity in the cuprate oxide is studied by Kondo-lattice theory based on the t – J model with the electron–phonon interaction arising from the modulation of the superexchange interaction by phonons. The self-energy of electrons is decomposed into the single-site and multisite self-energies. It is proved by using the mapping of the single-site self-energy in the t – J model to its corresponding one in the Anderson model that the single-site self-energy is simply that of a conventional Fermi liquid, even if a superconducting order parameter appears or the multisite self-energy is anomalous. The electron liquid characterized by the single-site self-energy is a conventional Fermi liquid. The Fermi liquid is further stabilized by the resonating-valence-bond (RVB) mechanism. The stabilized Fermi liquid is a relevant unperturbed state that can be used to study superconductivity and anomalous Fermi-liquid behaviors. The so-called spin-fluctuation-mediated exchange interaction, which includes the superex...