Summary
In the three-band Hubbard model, the fully symmetric Cu-O clusters with a central Cu and appropriate hole numbers have many-body ground states in which holes are paired. Here we investigate the mechanism of pairing, focusing on clusters with ≤ 21 atoms and 4 holes. We show that spin-flip diagrams yield the effective interaction. The analysis agrees with the results of exact diagonalization and shows that singlet-triplet splitting measures the strength of the pairing interaction. Moreover, the quantization at half-integer values of a magnetic text flux is consistent with supercon-ducting pairing.
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In honour of Prof. Gianfranco Chiarotti on the occasion of his 70th birthday.
This work has been supported by the Istituto Nazionale di Fisica della Materia. We acknowledge A. R. Bishop, Los Alamos Laboratories, USA, and R. Del Sole and G. Onida, Università di Roma II “Tor Vergata”, for useful discussions.
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Cini, M., Balzarotti, A. Hole pairing and flux quantization in modelCu-O clusters. Nouv Cim D 20, 1141–1146 (1998). https://doi.org/10.1007/BF03185523
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DOI: https://doi.org/10.1007/BF03185523