Exciton binding energy in the strong correlation limit of conjugated chains

Phys. Rev. B 58, 15329 – Published 15 December 1998
Z. Shuai, J. L. Brédas, S. K. Pati, and S. Ramasesha


By applying the numerically accurate symmetrized density-matrix renormalization-group method coupled with the extended Hubbard-Peierls model, we find that (i) the on-site Hubbard repulsion energy U dramatically reduces the binding energy of the lowest optically allowed 1Bu exciton; (ii) in the zero-dimerization limit, there exists a critical value of V at which the 1Bu exciton becomes bound; the critical value Vc=2t is fully in agreement with the recent analytical results at the infinite-U limit by Gallagher and Mazumdar [Phys. Rev. B 56, 15 025 (1997)], furthermore, this critical value decreases appreciably for weaker on-site correlation strengths, when the dimerization amplitude (δ) is nonzero. The present accurate numerical results contradict those obtained recently by Yu, Saxena, and Bishop [Phys. Rev. B 56, 3697 (1997)] both qualitatively and quantitatively. We also present first-order perturbation plus random-phase-approximation and single configuration-interaction analyses to rationalize the numerical calculations.

DOI: http://dx.doi.org/10.1103/PhysRevB.58.15329

  • Received 7 October 1997
  • Revised 9 June 1998
  • Published in the issue dated 15 December 1998

© 1998 The American Physical Society

Authors & Affiliations

Z. Shuai and J. L. Brédas

  • Centre de Recherche des Electronique et Photonique Moléculaires, Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc 20, 7000 Mons, Belgium

S. K. Pati and S. Ramasesha

  • Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India

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