Dielectric spectroscopy on the quasi-one-dimensional organic charge density wave conductor (Fluoranthene)₂PF₆

Abstract

Frequency-dependent complex conductivity measurements on the organic quasi-one-dimensional CDW system (Fa)2PF6 between 10-4 Hz and 3·109 Hz at temperatures ranging from 20 K to 290 K are reported. Below the temperature of the Peierls transition (Tp = 182K) the real part of the conductivity exhibits two structures, which can be attributed to two modes of the charge density wave (CDW): a temperature-dependent low-frequency relaxational mode of local oscillating deformations and a high-frequency resonant mode of the pinned CDW as a whole. The measurements indicate that the damping of the relaxational mode is dominated by free carriers in the covered temperature range. At low temperatures the dynamics of the CDW in (Fa)2PF6 shows features characteristic of the transition into a glass-like state.