Quantum transport in AuCl₃ doped polyacetylene studied by ESR

Starting with a review of general principles of transport processes in polyacetylene (PA) which can be studied by electron spin resonance (ESR) new results on highly doped PA are presented. The AuCl₃ doped PA samples stored under vacuum at room temperature in ESR sample tubes reach a steady state in the temperature dependent intensity and linewidth behavior after three to four month storage. The ESR spectra show two lines with an equal g-factor. In particular, the linewidth of the small line demonstrates a remarkable property. The temperature dependence of the linewidth shows a maximum of ΔB = 0.30 mT at 30 K, and it is constant at ΔB = 0.17 mT above this temperature in the whole temperature region between 70 and 300 K. The ESR data are discussed in a two spin model of delocalized states at the PA chain and fixed spins near the dopants. Broadening and motional narrowing influence the ESR linewidth. The interpretation points to the metallic behavior of the highly doped PA at low temperatures.