2003/09/30 by Tobias Baier, T. Baier, Eike Bick +2 · 2 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Physics of Superconductivity and Magnetism #Quantum many-body systems #cond-mat.str-el #cond-mat.supr-con #hep-th
paper · pdf · doi:10.1103/physrevb.70.125111
New section on critical behavior 31 pages,17 figures
arxiv created 2004/01/21 · openalex publication_date 2004/09/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The authors suggest an approximative solution of the two-dimensional Hubbard model close to half-filling. It is based on partial bosonization, supplemented by an investigation of the functional renormalization group flow. The inclusion of the fermionic and bosonic fluctuations leads in lowest order to agreement with Hartree-Fock result or Schwinger-Dyson equation and cures the mean field ambiguity. We compute the temperature dependence of the antiferromagnetic order parameter and the gap below the critical temperature. We argue that the Mermin-Wagner theorem is not practically applicable for the spontaneous breaking of the continuous spin symmetry in the antiferromagnetic state of the Hubbard model. The long distance behavior close to and below the critical temperature is governed by the renormalization flow for the effective interactions of composite Goldstone bosons and deviates strongly from the Hartree-Fock result.