We performed dielectric spectroscopy on polypyrrole near the metal-insulator transition (MIT) down to 2 K. We evaluate the dependence of the plasma frequency and the scattering time (t) on the distance to the MIT, characterized by the Fermi-level relative to the band-edge of extended states, E_F-E_c. Especially the strong decrease of t with increasing E_F-E_c is in conflict with the usually applied models for the MIT. Although morphology and disorder are important, the MIT is Mott-Hubbard-like being dominated by the competition of interchain charge transfer and electronic correlation.
@article{arxiv.cond-mat/0101178,
title = {Metal-insulator transition in PF6 doped polypyrrole: interchain charge transfer versus electronic correlation},
author = {H. C. F. Martens and H. B. Brom and R. Menon},
journal= {arXiv preprint arXiv:cond-mat/0101178},
year = {2007}
}