Low-frequency transport and relaxation of charge density waves in (TaSe4)2I crystals

Abstract

A charge density wave (CDW) occurs in low-dimensional solids as a consequence of the Peierls transition. Various field- and frequency-dependent effects, as well as those of excess noise, are related to CDW transport. We investigate low-frequency (10-10 6 Hz) dielectric relaxation as well as voltage fluctuations as a result of internal dynamic or sliding CDW in quasi one-dimensional chain compound (TaSe4)21 single crystals. The activation energy for normal conduction obtained from low field resistivity was ΔE = 0.122 ± 0.004eV. The most useful expression of dielectric relaxation for a strong damped system with one degree of freedom is e(ω) α(1 + iωτ 0 ) -1 , where relaxation times are distributed at the average τ 0 . τ 0 versus 1/T shows thermal activation ΔE = 0.124 ± 0.004eV. Voltage fluctuations produced by a sliding CDW are found to originate from random thermally activated transitions between metastable states. Noise power spectra between 500Hz and 600kHz at temperatures between 165 and 215K have S(f) α f -α dependence. The distribution of relaxation times and the temperature-dependent shortest relaxation time reflect CDW internal dynamics and the importance of free carriers on it.