open access

https://hdl.handle.net/2115/38994

Strong-Coupling Superconductivity in the Cuprate Oxide

英語

Kondo lattice

2009-08

Physical Society of Japan

Journal of the Physical Society of Japan

78(8)

084712

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 selfenergies. 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 superexchange interaction as a part, is the attractive interaction that binds d_[x2-y2]-wave Cooper pairs. An analysis of the spin susceptibility implies that, because of the electron-phonon interaction, the imaginary part of the exchange interaction has a sharp peak or dip at ±ω*, where ω* ⋍ ωph in the normal state and 1/2εG ≲ ω* ≲ 1/2εG + ωph in the superconducting state, where ωph is the energy of relevant phonons and εG is the superconducting gap. If the imaginary part has a sharp peak or dip at ±ω*, then the dispersion relation of quasi-particles has kink structures near ±ω* above and below the chemical potential, the density of states has dip-and-hump structures near ±ω* outside the coherence peaks in the superconducting state, and the anisotropy of the gap deviates from the simple d_[x2-y2]-wave anisotropy.

学術雑誌論文

Accepted Manuscript

© 2009 The Physical Society of Japan

0031-9015

AA00704814