Kinematic spin-fluctuation mechanism of high-temperature superconductivity

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 .