High-pressure low-temperature electrical properties of polypyrrole doped with p-toluenesulfonate

The electrical properties of polypyrrole doped with p-toluenesulfonate are investigated at temperatures from 300 to 1.2 K and pressures up to 2 GPa. A linear temperature dependence of the thermopower below 150 K supports the intrinsic metallic nature of the samples. The electrical conductivity shows the crossover from nearest-neighbour hopping to variable range hopping at low temperatures. Application of pressure results in a remarkable decrease of the localization strength of the charge carriers and a weaker temperature dependence of the conductivity.