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Millimeter-wave and far-infrared conductivity of iodine- and As F 5 -doped polyacetylene

1984; American Physical Society; Volume: 29; Issue: 8 Linguagem: Inglês

10.1103/physrevb.29.4595

1095-3795

L. Genzel, Friedrich Kremer, A. Poglitsch, G. Bechtold, Klaus Menke, S. Roth,

Mechanical and Optical Resonators

Dielectric measurements covering the frequency range from dc to the far infrared are reported for iodine- and As${\mathrm{F}}_{5}$-doped cis- and trans-polyacetylene, partly on the same batch of samples. The dispersion of the conductivity in the mm and sub-mm region suggests a superposition of a Drude free-carrier and a phonon-assisted hopping mechanism. In the sub-mm range the onset of an additional temperature-dependent absorption is found which does not freeze out completely at low temperatures. Most of this absorption is assigned to electronic transitions at the Fermi level. The temperature behavior of the conductivity, especially at mm-wave frequencies, is found to depend strongly on the doping species (iodine or As${\mathrm{F}}_{5}$) but much less on the isomeric state of the polymer (cis or trans). Hence, it is concluded that the predominant mechanism of electrical charge transport in polyacetylene does not involve mobile solitons.