Canonical BCS approximation for the attractive Hubbard model
作者:
K. Tanaka,
F. Marsiglio,
期刊:
AIP Conference Proceedings
(AIP Available online 1999)
卷期:
Volume 483,
issue 1
页码: 126-129
ISSN:0094-243X
年代: 1999
DOI:10.1063/1.59610
出版商: AIP
数据来源: AIP
摘要:
We test the canonical BCS wave functions for fixed number of electrons for the attractive Hubbard model. We present results in one dimension for various chain lengths, electron densities, and coupling strengths. The ground-state energy and energy gap to the first excited state are compared with the exact solutions obtained by the Bethe ansatz as well as with the results from the conventional grand-canonical BCS approximations. While the canonical and grand-canonical BCS results are both in very good agreement with the exact results for the ground state energies, improvements due to conserving the electron number in finite systems are manifest in the energy gap. As the system size is increased, the canonical results converge to the grand-canonical ones. The “parity” effect that arises from the number parity (even or odd) of electrons are studied with our canonical scheme. ©1999 American Institute of Physics.
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