1999/09/23 by A. Dorneich, M. G. Zacher, C. Groeber +2 · 1 citation
Physics and Astronomy · #Advanced Condensed Matter Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.61.12816
RevTex-file, 10 PRB pages with 6 eps figures. Hardcopies of figures (or the entire manuscript) can be obtained by e-mail request to: [email protected]
arxiv created 1999/09/23 · openalex publication_date 2000/05/15 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We reanalyze the Hubbard-I approximation by showing that it is equivalent to an effective Hamiltonian describing Fermionic charge fluctuations, which can be solved by Bogoliubov transformation. As the most important correction in the limit of large U and weak spin correlations we augment this Hamiltonian by further effective particles, which describe composite objects of a Fermionic charge fluctuation and a spin-, density-, or \ensuremathη excitation. The scheme is valid for positive and negative U. We present results for the single particle Green's function for the two-dimensional Hubbard model with and without t^\ensuremath' and t^\ensuremath'' terms, and compare to quantum Monte-Carlo results for the paramagnetic phase. The overall agreement is significantly improved over the conventional Hubbard-I or two-pole approximation.