Anomalous Frequency-Dependent Conductivity of Polyacetylene

The frequency ($f$) and temperature ($T$) dependent conductivity ($\sigma$) is reported for cis-${\left(\mathrm{CH}\right)}_x$, trans-${\left(\mathrm{CH}\right)}_x$, and ammonia-compensated ${\left(\mathrm{CH}\right)}_x$. A strongly $T$-dependent dc $\sigma$ together with a weakly $T$-dependent ac $\sigma$ were observed for predominantly cis-${\left(\mathrm{CH}\right)}_x$ and for N${\mathrm{H}}_3$-compensated samples, similar to $\sigma \mathrm{}(f,t)\mathrm{}$ of many semiconductors. The trans-${\left(\mathrm{CH}\right)}_x$ has a larger "weakly" $T$-dependent dc $\sigma$ and anomalous strongly $T$-dependent ac $\sigma$. The latter results are in good agreement with Kivelson's theory of charge transport via intersoliton electron hopping.