On the theory of superconductivity in the extended Hubbard model: Spin-fluctuation pairing

TL;DR

This paper develops a microscopic theory for superconductivity in the extended Hubbard model, highlighting spin-fluctuation mediated d-wave pairing with high critical temperatures in strongly correlated systems.

Contribution

It introduces a comprehensive approach considering intersite Coulomb repulsion and electron-phonon interactions within the Hubbard model, emphasizing spin-fluctuation pairing mechanisms.

Findings

High-Tc d-wave superconductivity mediated by spin fluctuations.

Intersite Coulomb repulsion and phonons have minor effects on pairing.

Strong correlations lead to narrow bandwidth and antiferromagnetic correlations.

Abstract

A microscopic theory of superconductivity in the extended Hubbard model which takes into account the intersite Coulomb repulsion and electron-phonon interaction is developed in the limit of strong correlations. The Dyson equation for normal and pair Green functions expressed in terms of the Hubbard operators is derived. The self-energy is obtained in the noncrossing approximation. In the normal state, antiferromagnetic short-range correlations result in the electronic spectrum with a narrow bandwidth. We calculate superconducting Tc by taking into account the pairing mediated by charge and spin fluctuations and phonons. We found the d-wave pairing with high-Tc mediated by spin fluctuations induced by the strong kinematic interaction for the Hubbard operators. Contributions to the d-wave pairing coming from the intersite Coulomb repulsion and phonons turned out to be small.