Solution for the U -negative Hubbard superconductor including second-order correlation effects

Journal Article · Mon Jun 01 04:00:00 EDT 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.13008· OSTI ID:7285636

Martin-Rodero, A; Flores, F ^[1]

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1. Departamento de Fisica de la Materia Condensada C-XII, Facultad de Ciencias, Universidad Autonoma, E-28049 Madrid (Spain)

We analyze the effects of fluctuations on the gap and critical temperature of a superconductor. The model Hamiltonian chosen is one of the simplest: the {ital U}-negative Hubbard model. A diagrammatic self-consistent approach is used, and a second-order self-energy is calculated in order to take into account local fluctuations. Our results show a decrease of the superconductor gap and critical temperature with respect to the mean-field solution. The ratio 2{Delta}/{ital k}{sub {ital B}T{ital c}} is not modified, however, by the local fluctuations if the self-energy matrix in a site representation extends only to the lattice nearest neighbors. In this approximation, the superconductor gap is found to be constant along the Fermi surface. Further nearest-neighbor interactions introduce a superconductor gap that changes along this surface.

• OSTI ID: 7285636
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 45:22; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ENERGY
ENERGY GAP
FLUCTUATIONS
MEAN-FIELD THEORY
PERTURBATION THEORY
PHYSICAL PROPERTIES
SELF-ENERGY
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VARIATIONS