Rigorous theorems on off-diagonal long-range order in the negative-UHubbard model
- 1 February 1992
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 45 (6) , 3145-3148
- https://doi.org/10.1103/physrevb.45.3145
Abstract
In this article, we study off-diagonal long-range order in the negative-U Hubbard model. We rigorously prove that all the elements of the two-particle reduced density matrix are positive, which may indicate a Bose condensation at q=0. Furthermore, we shall show that the ground state at half filling has pseudospin number 0. It implies that a sufficient condition proposed by Yang and Zhang [Int. J. Mod. Phys. B 5, 977 (1991)], for a state Ψ having off-diagonal long-range order, may not be a necessary condition.Keywords
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