Functional-integral approach to strongly correlated Fermi systems: Quantum fluctuations beyond the Gutzwiller approximation

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.142· OSTI ID:7034386

Lavagna, M ^[1]

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1. Institut Laue-Langevin, Boite Postale 156X, 38042 Grenoble CEDEX, France (FR)

A systematic extension of the model of almost localized fermions to finite temperatures is presented. It consists in accounting for the quantum fluctuations beyond the Gutzwiller approximation (GA). We use the slave-boson formulation of the Hubbard model which has been proved to be equivalent at the saddle-point level to the GA. We determine the values of the Lagrange multipliers introduced to enforce the constraints, and show how they involve a Mott gap at nearly half filling for {ital U}{gt}{ital U}{sub {ital c}} (localization edge). The results of the GA for the correlation functions are reproduced at the saddle point when taking into account the implicit dependence of the boson fields with the external excitation. The Gaussian fluctuations are then considered in a renormalized basis of the boson fields which brings out two distinct channels (symmetric {ital s} and antisymmetric {ital a}). We show how the free energy and the correlation functions can be simply expressed as a function of the same Landau parameters {ital F}{sub 0}{sup {ital s}} and {ital F}{sub 0}{sup {ital a}} defined in the GA.

• OSTI ID: 7034386
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:1; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

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