Canonical BCS approximation for the attractive Hubbard model | Zendy

К. Tanaka | Zendy; F. Marsiglio | Zendy

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Canonical BCS approximation for the attractive Hubbard model

Author(s) -

К. Tanaka,

F. Marsiglio

Publication year - 1999

Publication title -

aip conference proceedings

Language(s) - English

Resource type - Conference proceedings

eISSN - 1551-7616

pISSN - 0094-243X

DOI - 10.1063/1.59610

Subject(s) - ground state , grand canonical ensemble , hubbard model , physics , electron , canonical ensemble , excited state , parity (physics) , quantum mechanics , bethe ansatz , ansatz , statistical physics , mathematics , quantum , superconductivity , statistics , monte carlo method

We test the canonical BCS wave functions for fixed number of electrons forthe attractive Hubbard model. We present results in one dimension for variouschain lengths, electron densities, and coupling strengths. The ground-stateenergy and energy gap to the first excited state are compared with the exactsolutions obtained by the Bethe ansatz as well as with the results from theconventional grand-canonical BCS approximations. While the canonical andgrand-canonical BCS results are both in very good agreement with the exactresults for the ground state energies, improvements due to conserving theelectron number in finite systems are manifest in the energy gap. As the systemsize is increased, the canonical results converge to the grand-canonical ones.The ``parity'' effect that arises from the number parity (even or odd) ofelectrons are studied with our canonical scheme.Comment: 4 pages, 3 figures, HTS99 conference proceedin

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