Fourth-Order Perturbation Expansion for Hubbard Model on a Two-Dimensional Square Lattice
| dc.creator | Ikeda, H. | |
| dc.creator | Shinkai, S. | |
| dc.creator | Yamada, K. | |
| dc.date | 2008-10-10 | |
| dc.date.accessioned | 2026-07-07T10:09:07Z | |
| dc.date.available | 2026-07-07T10:09:07Z | |
| dc.description | We investigate the Hubbard model on a two-dimensional square lattice by the perturbation expansion to the fourth order in the on-site Coulomb repulsion U. Numerically calculating all diagrams up to the fourth order in self-energy, we examine the convergence of perturbation series in the lattice system. We indicate that the coefficient of each order term rapidly decreases as in the impurity Anderson model for T > 0.1t in the half-filled case, but it holds in the doped case even at lower temperatures. Thus, we can expect that the convergence of perturbation expansion in U is very good in a wide parameter region also in the lattice system, except for T < 0.1t in the half-filled case. We next calculate the density of states in the fourth-order perturbation. In the half-filled case, the shape in a moderate correlation regime is quite different from the three peak structure in the second-order perturbation. Remarkable upper and lower Hubbard bands locate at w = +(-)U/2, and a pseudogap appears at the Fermi level w=0. This is considered as the precursor of the Mott-Hubbard antiferromagnetic structure. In the doped case, quasiparticles with very heavy mass are formed at the Fermi level. Thus, we conclude that the fourth-order perturbation theory overall well explain the asymptotic behaviors in a strong correlation regime. | |
| dc.description | 17 pages, 20 figures | |
| dc.identifier | https://arxiv.org/abs/0810.1815 | |
| dc.identifier | http://arxiv.org/abs/0810.1815 | |
| dc.identifier | J. Phys. Soc. Jpn. 77, 064707 (2008) | |
| dc.identifier | doi:10.1143/JPSJ.77.064707 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/171223 | |
| dc.subject | Superconductivity | |
| dc.subject | Strongly Correlated Electrons | |
| dc.title | Fourth-Order Perturbation Expansion for Hubbard Model on a Two-Dimensional Square Lattice | |
| dc.type | text |