Abstract
A diagrammatic approach to the evaluation of correlated variational wave functions for strongly interacting fermions is presented. Diagrammatic rules for the calculation of the one-particle density matrix and the Hubbard interaction are derived which are valid for arbitraryd-dimensional lattices. An exact evaluation of expectation values is performed in the limitd=∞. The wellknown Gutzwiller approximation is seen to become the exact result for the expectation value of the Hubbard Hamiltonian in terms of the Gutzwiller wave function ind=∞. An efficient procedure to correct the Gutzwiller approximation in finite dimensions is developed. A detailed discussion of expectation values ind=∞ in terms of explicit antiferromagnetic wave functions is given. Thereby an approximate result for the ground state energy of the Hubbard model, obtained recently within a slave-boson approach, is recovered.
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The graphs used here differ slightly from the graphs described in Ref. 11,. Lines are now directed by an arrow and the spin is indicated by a free spin variable (not by drawing two types of lines) which has to be summed up. In this way one no longer needs to bother about the rather complicated “weight factors” introduced in Ref. 11. Metzner, W., Vollhardt, D.: Phys. Rev. Lett59, 121 (1987); Phys. Rev. B37, 7382 (1988)
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I am grateful to F. Gebhard for pointing this out to me
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Metzner, W.: (unpublished)
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Fazekas, P.: Preprint (submitted to Phys. Scr.)
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Metzner, W. Variational theory for correlated lattice fermions in high dimensions. Z. Physik B - Condensed Matter 77, 253–266 (1989). https://doi.org/10.1007/BF01313669
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DOI: https://doi.org/10.1007/BF01313669