Abstract:
We study the Cu5O4 cluster by exact diagonalization of a three-band Hubbard model and show that bound electron or hole pairs are obtained at appropriate fillings, and produce superconducting flux quantization. The results extend earlier cluster studies and illustrate a canonical transformation approach to pairing that we have developed recently for the full plane. The quasiparticles that in the many-body problem behave like Cooper pairs are W =0 pairs, that is, two-hole eigenstates of the Hubbard Hamiltonian with vanishing on-site repulsion. The cluster allows W =0 pairs of d symmetry, due to a spin fluctuation, and ssymmetry, due to a charge fluctuation. Flux quantization is shown to be a manifestation of symmetry properties that hold for clusters of arbitrary size.
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Received 23 July 1999
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Cini, M., Balzarotti, A. & Stefanucci, G. Pairing in the Hubbard model: the Cu O cluster versus the Cu-O plane. Eur. Phys. J. B 14, 269–280 (2000). https://doi.org/10.1007/s100510050129
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DOI: https://doi.org/10.1007/s100510050129