Phys. Rev. B 69, 155109 (2004) [10 pages]Effect of Hund coupling in the one-dimensional SU(4) Hubbard modelReceived 19 February 2003; revised 29 September 2003; published 15 April 2004 The one-dimensional SU(4) Hubbard model perturbed by Hund coupling is studied, away from half-filling, by means of renormalization-group and bosonization methods. A spectral gap is always present in the spin-orbital sector irrespective of the magnitude of the Coulomb repulsion. We further distinguish between two qualitatively different regimes. At small Hund coupling, we find that the symmetry of the system is dynamically enlarged to SU(4) at low energy with the result of coherent spin-orbital excitations. When the charge sector is not gapped, a superconducting instability is shown to exist. At large Hund coupling, the symmetry is no longer enlarged to SU(4) and the excitations in the spin sector become incoherent. Furthermore, the superconductivity can be suppressed in favor of the conventional charge density wave state. © 2004 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevB.69.155109
DOI:
10.1103/PhysRevB.69.155109
PACS:
71.10.Hf, 75.10.Jm, 78.67.Lt
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