Logarithmic temperature dependence of resistivity in heavily doped conducting polymers at low temperature

Electrical resistivities of heavily doped polyacetylene and polypyrrole exhibit a wide range of temperature variation as a function of the degree of disorder. Thermal activation behavior is found for the strongly disordered state, while a weak temperature dependence down to the mK region is found for the weakly disordered state. In the intermediate region we found the resistivity represented by a logT dependence, in a manner similar to amorphous metals. As a cause of the logT dependence, the possibility of scattering via interaction with molecular configurations possessing low-energy internal degrees of freedom is considered.