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An exact study of pairing fluctuations and phase diagrams in four-site Hubbard Nanoclusters

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Journal of Computer-Aided Materials Design

Abstract

Charge-spin separation and pairing fluctuations and pseudogaps are studied using the analytical eigenvalues of the four-site Hubbard Nanoclusters with the grand canonical and canonical ensemble approaches in a multidimensional parameter space of temperature (T), magnetic field (h), on-site interaction (U), chemical potential (μ), and number of electrons (N). The electron charge energy gap, with one hole off half filling, corresponds to an excitonic particle–hole pair binding energy Δe-h > 0 at U > U c and vanishes at a critical parameter U c =  4.584. For U < U c, particle–particle pair binding is found with a pairing energy Δp > 0. In addition, for U ⩽ U c we find an electron pair binding instability at finite temperature near N ≈ 3, which manifests a possible pairing mechanism, a precursor to superconductivity, in small clusters. The resulting phase diagram, consisting of charge and spin pseudogaps, hole pairing near 1/8th filling with hole-rich and hole-poor regions in the ensemble of Nanoclusters, closely resembles the phase diagrams in the family of doped high-T c-cuprates.

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Authors and Affiliations

  1. Department of Physics, University of Connecticut, Storrs, CT, 06269-3046, USA

    Kalum Palandage & Gayanath W. Fernando

  2. Department of Physics and Astronomy, California State University, Northridge, CA, 91330-8268, USA

    Armen N. Kocharian

  3. Computational science center, Brookhaven National Laboratory, Upton, NY, 11973, USA

    James W. Davenport

Authors
  1. Kalum Palandage
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  2. Gayanath W. Fernando
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  3. Armen N. Kocharian
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  4. James W. Davenport
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Correspondence to Gayanath W. Fernando.

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Palandage, K., Fernando, G.W., Kocharian, A.N. et al. An exact study of pairing fluctuations and phase diagrams in four-site Hubbard Nanoclusters. J Computer-Aided Mater Des 14, 103–108 (2007). https://doi.org/10.1007/s10820-006-9024-y

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  • DOI: https://doi.org/10.1007/s10820-006-9024-y

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