Metallic properties of transition metal halides doped polyacetylene: The soliton liquid state

Abstract

Temperature dependence of d.c. conductivity and thermoelectric power (TEP) are measured for the newly processed polyacetylenes doped with FeCl 3, MoCl 5, NbCl 5 and ZrCl 4. The data can be analyzed as followings. (1) The metallic polyacetylene shows quasi-one-dimensional charge transport mechanism. To support this conclusion, we compared the temperature dependent anisotropy of conductivity for the nondegenerate ground state conducting polymers such as PPV derivatives. (2) TEP data indicate that there exists an interaction between the delocalized charge carrier in the polymer chain and the dopant ions located nearby the chain. As a consistent interpretation, we propose that the metallic polyacetylene is formed by the soliton - antisoliton condensation (we call this as soliton liquid state). With this proposal, both the Pauli susceptibility and the infrared active vibrational modes (IRAV) observed in the metallic polyacetylene can be understood simultaneously.