ANALYSIS OF THE DC CONDUCTIVITY OF THE QUASI-ONE-DIMENSIONAL CHARGE-DENSITY-WAVE CONDUCTOR (FLUORANTHENE)(2)X

It has been shown recently that the dc conductivity (along the highly conducting axis) of fluoranthene radical cation salts exhibits the beh avior of a quasi-one-dimensional conductor with a Peierls transition a t about 180 K to a charge-density-wave ground state. In the high-tempe rature range fluctuations of the order parameter lead to a pseudogap i n the electronic density of states, whereas below the phase transition the energy gap is BCS-like. To analyze the conductivity data, a simpl e band-structure model is used and related to optical data. In spite o f the occurrence of the Peierls transition, it is assumed that three-d imensional effects and fluctuations are strong enough for the conducti on to be essentially due to electron-hole transport in bands and not p olaronlike. Therefore the conductivity is determined simply by the Bol tzmann equation with deformation-potential scattering. (a) This model yields a good fit of experimental data using the BCS-like gap below th e transition and the pseudogap as determined from paramagnetic spin su sceptibility above the transition. (b) It is possible to obtain the te mperature dependence of the concentration, the mobility, the relaxatio n time, and the mean free path of carriers. (c) One can check a fundam ental criterion for the applicability of the model. (d) We obtain from the fit parameters reasonable estimates of the quantities determining the deformation-potential scattering. Moreover, it is demonstrated th at the theory pan be used to determine the full temperature dependence of the gap/pseudogap directly from conductivity data,