Charge transport and electrodynamic response of a conducting polymer

Conducting organic polymers exhibit a wide range of conductivity based on protonation levels, similar to that of semiconductor materials upon impurity doping. The conducting polymer polyaniline (PANI) can be synthesized in this manner easily and economically The conductivity of protonated PANI can be systematically tuned from a highly insulating state to one exhibiting qualitatively metallic charge transport, passing through the metal-insulator transition (MIT) along the way. This tunable material provides a rich environment in which to explore charge transport in the viscinity of a quantum phase transition. In this study, I present novel measurements of the optical conductivity, o(w) = o₁(w) + io₂(w), of insulating polyaniline protonated with Hydrochloric acid (PANI-HC1) in the terahertz (THz) range as well as the temperature-dependent DC conductivity, oDC(T), and show that the results are consistent with theories incorporating electron-electron correlations.