Quantum transport in AuCl3 doped polyacetylene studied by ESR

Starting with a review of general principles of transport processes in poly acetylene (PA) which can be studied by electron spin resonance (ESR) new re sults on highly doped PA are presented. The AuCl3 doped PA samples stored u nder 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 pr operty. The temperature dependence of the linewidth shows a maximum of Delt aB = 0.30 mT at 30 K, and it is constant at DeltaB = 0.17 mT above this tem perature 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 an d fixed spins near the dopants. Broadening and motional narrowing influence the ESR linewidth. The interpretation points to the metallic behavior of t he highly doped PA at low temperatures. (C) 2001 Elsevier Science B.V. All rights reserved.