Determination of Correlation Parameters in π-Conjugated Polymers

Abstract

Using exact finite-size diagonalizations of extended Peierls-Hubbard Hamiltonians for systems of up to 15 sites, we study the excited state spectra of models for the finite oligomer analogs of trans– and cis– polyacetylene. We use a novel “phase randomization” technique and a variety of other methods to extract maximal information from these small systems. For several electron-phonon couplings in the expected range, we discuss the extent to which we are able to find consistent values of the Hubbard on-site (U) and nearest-neighbor (V) correlation parameters such that the band gap, the 2 1Ag state, optical phonon frequency, and the optical absorptions for charged and neutral solitons and dimers occur in the experimentally expected ranges. Our results suggest that these correlation parameters are in the intermediate coupling regime (U ⋍ 2.5t0), beyond the range of perturbation theory.

This is a preview of subscription content, access via your institution.

References

  1. 1.

    For a recent review of the ePH Hamiltonian applied to (CH)x, see: D. Baeriswyl, D. K. Campbell, and S. Mazumdar, to be published in Conducting Polymers, edited by H. Kiess (Springer, New York, 1990).

  2. 2.

    See, e.g., the section on Lanczos diagonalization in S. Pissanetsky, Sparse Matrix Technology (Academic, London, 1984).

    Google Scholar 

  3. 3.

    D. K. Campbell, J. Tinka Gammel, and E. Y. Loh, Jr., to be published in the Proceedings of the Anniversary Adriatico Research Conference on Strongly Correlated Electrons, Trieste, Italy, July 18–21, 1989.

  4. 4.

    W.P. Su, J.R. Schrieffer, and A.J. Heeger, Phys. Rev. Lett. 42, 1698 (1979); Phys. Rev. Β 22, 2099 (1980).

    CAS  Article  Google Scholar 

  5. 5.

    P. F. Maldague, Phys. Rev. Β 16, 2437 (1977).

    CAS  Article  Google Scholar 

  6. 6.

    S. Κ. Lyo and J.-P. Gallinar, J. Phys. C. 10, 1693 (1977).

    CAS  Article  Google Scholar 

  7. 7.

    J.C.W. Chien, F.E. Karasz, and K. Shimamura, Makromol. Chem. Rapid Commun. 3, 655 (1982).

    CAS  Article  Google Scholar 

  8. 8.

    Ε. Ehrenfreund, Ζ. Vardeny, O. Brafman, and B. Horovitz, Phys. Rev. Β 36, 1535 (1987).

    CAS  Article  Google Scholar 

Download references

Author information

Affiliations

Authors

Corresponding author

Correspondence to J. Tinka Gammel.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Gammel, J., Campbell, D.K., Loh, E.Y. et al. Determination of Correlation Parameters in π-Conjugated Polymers. MRS Online Proceedings Library 173, 419–424 (1989). https://doi.org/10.1557/PROC-173-419

Download citation