Eur. Phys. J. B (2013) 86: 115
https://doi.org/10.1140/epjb/e2013-31157-6

Regular Article

On the theory of superconductivity in the extended Hubbard model

Spin-fluctuation pairing

¹ Joint Institute for Nuclear Research, 141980 Dubna, Russia
² Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
³ Rutgers University, 08854 New Jersey, USA

^a e-mail: plakida@theor.jinr.ru

Received: 27 December 2012
Received in final form: 17 January 2013
Published online: 25 March 2013

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 T_c by taking into account the pairing mediated by charge and spin fluctuations and phonons. We found the d-wave pairing with high-T_c 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.