Ground-state and excitation spectra of the negative- U Hubbard model

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

DOI:https://doi.org/10.1103/PhysRevB.45.10549· OSTI ID:7297533

Castillo, H E; Balseiro, C A ^[1]

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1. Centro Atomico Bariloche and Instituto Balseiro, 8400 San Carlos de Bariloche (Argentina)

We study the negative-{ital U} Hubbard model by exact diagonalization of a 4{times}4 cluster with different numbers of particles. We calculate the ground-state energy and wave function as well as the one-particle, charge- and spin-excitation spectra. We show that the BCS approximation gives results in good agreement with the exact ones for the ground-state energy and wave function in the whole range of {ital U}. In the one-particle excitation spectrum the BCS dispersion relation gives the position of the most intense peaks of the exact calculation. Lower-energy (quasiparticle) excitations, which are interpreted as strongly dressed Bogoliubov quasiparticles, also appear. The occurrence of pair-breaking and collective excitations in the charge- and spin-excitation spectra and the interplay between one-particle and collective modes are discussed.

• OSTI ID: 7297533
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 45:18; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BCS THEORY
COLLECTIVE EXCITATIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ENERGY LEVELS
ENERGY SPECTRA
ENERGY-LEVEL TRANSITIONS
EXCITATION
FUNCTIONS
GROUND STATES
NUMERICAL SOLUTION
PHYSICAL PROPERTIES
SPECTRA
SUPERCONDUCTIVITY
WAVE FUNCTIONS