Europhys. Lett.
Volume 68, Number 6, December 2004
Page(s) 839 - 845
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 12 November 2004
Europhys. Lett., 68 (6), pp. 839-845 (2004)
DOI: 10.1209/epl/i2004-10273-7

Superconductivity driven by chain coupling and electronic correlations

J. M. P. Carmelo1, 2, F. Guinea3, K. Penc4 and P. D. Sacramento5

1  Department of Physics, MIT - Cambridge, MA 02139-4307, USA
2  GCEP-Center of Physics, U. Minho - Campus Gualtar, P-4710-057 Braga, Portugal
3  Instituto de Ciencia de Materiales, CSIC - Cantoblanco, E-28949 Madrid, Spain
4  Research Institute for Solid State Physics and Optics H-1525 Budapest, P.O.B. 49, Hungary
5  CFIF-Instituto Superior Técnico - Av. Rovisco Pais, 1049-001 Lisboa, Portugal

received 24 May 2004; accepted in final form 14 October 2004
published online 12 November 2004

We present an analysis of a system of weakly coupled Hubbard chains based on combining an exact study of spectral functions of the uncoupled-chain system with a renormalization group method for the coupled chains. For low values of the onsite repulsion U and of the doping $\delta$, the leading instability is towards a superconducting state. The process includes excited states above a small correlation pseudogap. Similar features appear in extended Hubbard models in the vicinity of commensurate fillings. Our theoretical predictions are consistent with the phase diagram observed in the (TMTTF) 2X and (TMTSF) 2X series of organic compounds.

71.10.Pm - Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.).
74.20.Mn - Nonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.).
71.10.Li - Excited states and pairing interactions in model systems.

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