The temperature ($T$), frequency ($f$), and electric field ($E$) dependent conductivity ($\sigma$) of iodine-doped polyacetylene is reported for the concentration regime which encompasses the metal-insulator transition. No $f$ dependence was observed for $f<\mathrm{}500\mathrm{}$ MHz. The resistance varied logarithmically with $E$, while $\sigma \sim \ln T$ and $\sigma \sim \exp [-{\left(\frac{T_A}{T}\right)}^{0.25}]$ were observed. This $\sigma \mathrm{}(T,E,f)\mathrm{}$ is inconsistent with simple models of metallic regions separated by large barriers and suggests that the known strong disorder plays a dominant role.

• Received 19 June 1980

DOI:https://doi.org/10.1103/PhysRevLett.45.1730