Crossover from Cooper pairs to composite bosons: A generalized RPA analysis of collective excitations

Journal Article · Tue Mar 01 04:00:00 EST 1994 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.49.6829· OSTI ID:142611

Belkhir, L ^[1]; Randeria, M ^[2]

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1. Department of Physics, State University of New York, Stony Brook, New York 11794-3800 (United States)
2. Argonne National Laboratory, MSD 223, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

We study the evolution of the ground state and the excitation spectrum of the two- and three-dimensional attractive (negative-{ital U}) Hubbard model as the system evolves from a Cooper-pair regime for {ital U}{much_lt}{ital t}, to a composite boson regime for {ital U}{much_gt}{ital t}. Our work is motivated by the observation that the high-temperature superconductors, with their short coherence lengths and unusual normal-state properties, may be in an intermediate coupling regime between these two limits. A mean-field analysis of pairing, suitably generalized to account for a shift in the chemical potential, is known to be able to describe the ground-state crossover as a function of {ital U}/{ital t}. We compute the collective-mode spectrum using a generalized random-phase-approximation analysis within the equations-of-motion formalism. We find a smooth evolution of the Anderson mode for weak coupling into the Bogoliubov sound mode for hard-core bosons. We then include a long-range Coulomb interaction and show that it leads to a plasmon which again evolves smoothly from weak to strong coupling.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 142611
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 10 Vol. 49; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BOSONS
COLLECTIVE EXCITATIONS
COOPER PAIRS
COULOMB CORRECTION
EQUATIONS OF MOTION
GROUND STATES
HUBBARD MODEL
RANDOM PHASE APPROXIMATION
SUPERCONDUCTIVITY