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Modern Physics Letters B

ON THE THEORY OF SUPERCONDUCTIVITY IN THE HUBBARD MODEL

Nikolay M. Plakida, Ihor V. Stasyuk

Published Sep 1, 1988• 10 citations
Publisher

Abstract

A pairing mechanism caused by the kinematical interaction in the Hubbard model is considered. On the basis of equations of motion for two-time Green functions with anomalous pairings taken into account, equations are derived for the superconducting gap of an extended S-type and T c .
DOI
10.1142/s0217984988000771

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A microscopic theory of electronic spectrum and superconducting pairing within the Hubbard model is formulated.The Dyson equation for the normal and anomalous Green functions in terms of the Hubbard operators is derived by applying the Mori-type projection technique.The self-energy is evaluated in the noncrossing approximation for electron scattering on spin and charge fluctuations induced by kinematic interaction for Hubbard operators.Numerical results for electron dispersion in the strong correlation limit are presented.Superconducting pairing mediated by antiferromagnetic exchange and spin fluctuations is discussed.
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We study d-wave superconductivity in the extended Hubbard model in the strong correlation limit for a large intersite Coulomb repulsion V. We argue that in the Mott-Hubbard regime with two Hubbard subbands, there emerges a new energy scale for the spin-fluctuation coupling of electrons of the order of the electron kinetic energy W much larger than the exchange energy J. This coupling is induced by the kinematic interaction for the Hubbard operators, which results in the kinematic spin-fluctuation pairing mechanism for V ≲ W. The theory is based on the Mori projection technique in the equation of motion method for the Green’s functions in terms of the Hubbard operators. The doping dependence of the superconductivity temperature T c is calculated for various values of U and V.