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Binding energy of $1B_u$ singlet excitons in the one-dimensional extended Hubbard-Peierls model

Shuai, Z and Pati, Swapan K and Su, WP and Bredas, JL and Ramasesha, S (1997) Binding energy of $1B_u$ singlet excitons in the one-dimensional extended Hubbard-Peierls model. In: Physical Review B, 55 (23). pp. 15368-15371.

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Using a symmetrized density-matrix renormalization-group formulation, we have investigated the electronic binding energy of the lowest optically allowed exciton (1B(u)) within an extended Hubbard-Peierls model (with parameters U, V, and delta) for conjugated chains with N = 80 sites. Three symmetries, the C-2, spin parity, and electron-hole symmetries, have been applied to construct the projector operator. Analysis of our results on the ratios between exciton binding energies and exciton energies, sheds light on the current experimental and theoretical controversy on exciton binding for polyacetylene and polyparaphenylene vinylene. We show that in the absence of dimerization, the exciton binding energy is vanishingly small for U/t up to 5 and V/t up to 2.3; for a finite dimerization. it is only when V is large enough that the exciton gets to be significantly bound. This result questions the applicability to conjugated polymers of the strong correlation picture, in which the exciton binding energy is equal to V.

Item Type: Journal Article
Publication: Physical Review B
Publisher: American Physical Society
Additional Information: Copyright of this article belongs to American Physical Society
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 09 Mar 2009 05:59
Last Modified: 19 Sep 2010 05:02
URI: http://eprints.iisc.ac.in/id/eprint/18441

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