Phase diagram of the one-dimensional extended Hubbard model with attractive and/or repulsive interactions at quarter filling

Karlo Penc and Frédéric Mila
Phys. Rev. B 49, 9670 – Published 1 April 1994
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Abstract

We study the phase diagram of the one-dimensional U-V model at quarter filling in the most general case where the on-site and first-neighbor interactions U and V can be both attractive and repulsive. The results have been obtained using exact diagonalization of small clusters and variational techniques, as well as exact results in various limits. We have analyzed four properties of the ground state: (i) whether it is insulating or metallic; (ii) whether it is homogeneous or phase separated; (iii) whether it has a spin gap; (iv) whether it has dominant superconducting fluctuations. With eight phases, the resulting phase diagram is unexpectedly rich. The four phases not found in the weak coupling limit are: (i) an insulating phase when U and V are large enough; (ii) a region of phase separation when V is attractive; (iii) another region of phase separation when V is large enough and U small; (iv) a region with dominant superconducting fluctuations when V is intermediate and U small. The actual nature of this last plase, which has pairs but no spin gap, is not fully clear yet.

  • Received 29 November 1993

DOI:https://doi.org/10.1103/PhysRevB.49.9670

©1994 American Physical Society

Authors & Affiliations

Karlo Penc

  • Institut de Physique, Université de Neuchâtel, 1 Rue Breguet, CH-2000 Neuchâtel, Switzerland

Frédéric Mila

  • Laboratoire de Physique Quantique, Université Paul Sabatier, 31062 Toulouse, France

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Vol. 49, Iss. 14 — 1 April 1994

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