Metallic temperature dependence of resistivity in heavily doped polyacetylene by NMR

Abstract

Summary form only given. H-NMR spin-lattice relaxation rate T/sub 1//sup -1/ of heavily doped polyacetylene was measured in an attempt to study the spin dynamics of its conduction electrons. Films synthesized by standard Shirakawa method and non-solvent method were doped with FSO/sub 3/H, HClO/sub 4/, iodine, bromine and potassium in vapor phase. Against our intention, in all of the samples a metallic behavior in the T/sub 1//sup -1/ arising from quasi-one-dimensional motion of conduction electrons was not found for some time after doping, and it was revealed that the T/sub 1//sup -1/ was governed by a relaxation mechanism due to residual Curie spins. The results of T/sub 1//sup -1/ for the samples other than the bromine-doped sample did not show the metallic behavior after all, whereas for the bromine-doped one a change in the temperature dependence of T/sub 1//sup -1/ from the non-metallic behavior to the metallic one was found as time passed. It was confirmed that this change was caused by the partial substitution of hydrogen atoms in the polyacetylene chain by bromine atoms. We first succeeded in deducing the temperature dependence of intrinsic resistivity for metallic polyacetylene from the data of T/sub 1/sup -1/.