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

Abstract

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.

Superconductivity in metal-mixed ion-implanted polymer films

“…2 Conducting polymers such as heavily doped polyacetylene can exhibit a metallic state. 3,4 However, metallic behavior in organic polymers is not common, and the underlying physics is not well understood. 5 Ion implantation of normally insulating polymers offers an alternative to depositing metals or conjugated organics onto plastic films to make electronic circuits.…”

Emulating weak localization using a solid-state quantum circuit

“…To measure the return probability P return as a function of disorder, we average 100 random detuning pulse sequences with different distributions of t total , where t total is randomly generated from a Gaussian distribution with width s. Correlating the disorder with s, we simulate weak localization at increasing disorder levels by reducing s from 100 to 50 to 25 ns. In this way, we directly and separately tune the level of disorder, in contrast with the mesoscopic system where tuning the disorder level typically changes other parameters such as carrier density [30][31][32] . We note that adjusting s by itself is only valid for emulating disorder in our special case, where only time-reversed symmetric pairs are considered in the emulation.…”

Electron-ion interaction in doped conducting polymers

“…9,10 In the last decade, remarkable progress was made in stabilizing the highly conducting state in heavily doped conjugated polymers. A finite residual conductivity at very low temperatures down to 10 mK was successfully attained for heavily doped polymers 11 ͑for recent reviews see, e.g., Refs. 12 and 13͒.…”

“…The experiments also indicate that in spite of the large value of RT and finite residual conductivity, these highly conducting polymers are still far from being typical metals, e.g., the conductivity of most of samples still continues to decrease with decreasing temperature. Therefore, it was suggested [11][12][13] that this latest generation of conducting polymers is close to insulator-metal transition ͑IMT͒ which, in according with the general consensus, is an Anderson type of the disorder-driven localization-delocalization transition. 8 Through a small increase of disorder, e.g., with aging, the polymers often can be driven into the insulator state.…”

“…The resonance hopping among metallic grains can explain the low-frequency anomaly of electromagnetic response in the metallic phase. 11,12 The low concentration of charge carriers participating in dc transport corresponds to the small probability of finding those resonance states and the long relaxation time of electric response is related to the narrow width of the resonance levels.…”