Non-Ohmic Behavior ofcis-Polyacetylene Doped with AsF5

Detailed conductivity measurements on cis-${\left(\mathrm{CH}\right)}_x$ doped with As${\mathrm{F}}_5$ as a function of electric field for various temperatures are reported. For concentrations well below the semiconductor to metal transition, an exponential dependence of the resistance on the reciprocal of the electric field is observed. This result is consistent with a model of metallic domains embedded in a dielectric. It is their charging energy which determines both the temperature dependence and the field dependence of the conductivity. Non-Ohmic effects for concentrations above the transition are also discussed.