1993/10/11 by Lotfi Belkhir, Mohit Randeria · 64 citations
Mathematics · Physics and Astronomy · #Attraction #Boson #Cold Atom Physics and Bose-Einstein Condensates #Composite number #Computer science #Condensed matter physics #Cooper pair #Crossover #Excitation #Mathematics #Physics #Physics of Superconductivity and Magnetism #Quantum many-body systems #Quantum mechanics #Spectrum (functional analysis) #Statistical physics #Superconductivity #cond-mat
paper · pdf · doi:10.1103/physrevb.49.6829
published in Physical review. B, Condensed matter 49(10), 6829-6840 (American Physical Society) · 20 pages RevTex, 7 figures on request
arxiv created 1993/10/11 · openalex publication_date 1994/03/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We study the evolution of the ground state and the excitation spectrum of the two- and three-dimensional attractive (negative-U) Hubbard model as the system evolves from a Cooper-pair regime for U\ensuremath≪t, to a composite boson regime for U\ensuremath≫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 U/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.