The phase diagram of the Hubbard model is studied at weak coupling in two and three spatial dimensions. It is shown that the Néel temperature and the order parameter in d=3 are smaller than the Hartree-Fock predictions by a factor of q=0.2599. For d=2 we show that the self-consistent (sc) perturbation series bears no relevance to the behavior of the exact solution of the Hubbard model in the symmetry-broken phase. We also investigate an anisotropic model and show that the coupling between planes is essential for the validity of mean-field-type order parameters.
Physical Review B
- Pub Date:
- February 2002
- Lattice fermion models;
- Band and itinerant models;
- Condensed Matter - Strongly Correlated Electrons
- Phys. Rev. B 65, 081105(R) (2002)