Superconducting correlations in the one-band Hubbard model with intermediate on-site and weak attractive intersite interactions

K. P. Jain; R. Ramakumar; C. C. Chancey

doi:10.1103/PhysRevB.42.9896

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Superconducting correlations in the one-band Hubbard model with intermediate on-site and weak attractive intersite interactions

K. P. Jain, R. Ramakumar, C. C. Chancey

DOI 10.1103/PhysRevB.42.9896 · Physical Review B

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Abstract

In this paper, we analyze a simple extended Hubbard model with an intermediate on-site interaction (both repulsive and attractive) and a weak intersite attractive interaction. Following Hubbard decoupling approximations and introducing Hubbard subband operators, we obtain a generalized gap function for singlet s-wave pairing that explicitly depends on the Hubbard subband energies. For the on-site repulsive-interaction case, we find that the superconductivity is not destroyed in the intermediate-interaction regime, contrary to the prediction of a Hartree-Fock mean-field treatment. The essential consequence of the on-site repulsion is the formation of the Hubbard subbands separated by the Mott-Hubbard gap, and it is within these subbands that pairing induced by the intersite interaction occurs. For the attractive on-site interaction case, the on-site pairing amplitude is found to be proportional to the bandwidth, and the gap function has contributions from both on-site and intersite pairing. The relevance of the model to high-temperature superconductivity is discussed.