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Physical review. B, Condensed matter

Chemical potential and order parameter of extended Hubbard model with strong intra-atomic attraction

S. Robaszkiewicz, R. Micnas, K. A. Chao

Published Aug 1, 1981• 59 citations
Publisher

Abstract

We provide here the numerical solutions for the quasiparticle chemical potential and for the order parameters of the singlet-superconducting, the charge-ordered, and the mixed phases in an extended Hubbard model with strong intra-atomic attraction, based on the analysis of our previous paper.
DOI
10.1103/physrevb.24.1579

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We have investigated the ground-state properties of the negative-UUU extended Hubbard model in the weak-coupling regime with the Hartree theory formulated in terms of the Bogoliubov variational approach. While the pure phases of charge order (CO), singlet superconducting (SS), and nonordered can be solved analytically with a model density of states, the mixed phase of CO and SS requires numerical computation. The ground-state phase diagram is derived, and the order parameters and the chemical potential of the ground state are analyzed. The characteristic difference between the behaviors of the SS and the CO order parameters at very weak coupling suggests a complicated competition between various interactions. Present results are compared with those derived earlier for the strong-coupling regime.
The zero-temperature Hartree theory is extended to finite temperature to investigate the phase diagram, the order parameters, and the chemical potential of the negative-UUU extended Hubbard model in the weak-coupling regime. All the transitions between the charge-ordered, the singlet-superconducting, the mixed, and the nonordered phases are second order. In a special region of the parameter space, we discover the heat-charge-order process, which is the main source for the qualitative difference between the results of the present weak-coupling regime and the strong-coupling regime investigated earlier. Phenomena associated with the heat-charge order are compared to other work in which an effect similar to the heat-charge order exists.
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