1997/10/04 by J. J. Rodriguez - Nunez, Juana Nunez, Nunez, J. J. Rodriguez - +4
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Condensed Matter (cond-mat) #FOS: Physical sciences #Physics of Superconductivity and Magnetism #Quantum many-body systems #cond-mat
paper · pdf · doi:10.48550/arxiv.cond-mat/9710047
4 pages, three figures in ps (windows95). To appear in Physica A. Presented at LAWNP'97
arxiv created 1997/10/04 · openalex publication_date 1997/10/04 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We use the moment approach of Nolting (exact sum rules) (Z. Physik 255, 25 (1972)) for the attractive Hubbard model in the superconducting phase. Our diagonal and off - diagonal spectral functions are constructed and evaluated with the sum rules. They reduce to the BCS limit for weak interaction. However, the presence of correlations modify the BCS picture dramatically. For example, due to the presence of correlations we have postulated a three - pole ansatz for the diagonal Green function, G(k,ω), while the off - diagonal one, B(k,ω), is supposed to have two poles. In the paper we present results for the three spectral weights of the diagonal Green function, αj(k), j = 1,2,3. Our results compare reasonably well with more elaborated auto - consistent highly non - linear equations (double fluctuation calculations in the T- Matrix approach of one of the authors). Then, the physical picture which emerges is that the lower Hubbard band is split due to the superconducting gap and the upper Hubbard band remains mostly unmodified.