Energy-dependent hopping in trans-polyacetylene: Experiment and theory for complex conductivity

Measurements of dc conductivity and both parts of the complex ac conductivity are reported for $\text{trans}$-polyacetylene. The imaginary part is obtained by identifying the residual capacitance of the material. The data is analysed in terms of hopping transport, modelled by rate equations. An energy-dependent transition rate with an appropriate density of states gives a good account of the data. This is compared with results obtained when Kivelson's energy-independent rate is used.