LOW-FREQUENCY TRANSPORT AND RELAXATION OF CHARGE-DENSITY WAVES IN (TASE4)(2)I CRYSTALS

A charge density wave (CDW) occurs in low-dimensional solids as a cons equence of the Peierls transition. Various field- and frequency-depend ent effects, as well as those of excess noise, are related to CDW tran sport. We investigate low-frequency (10-10(6) Hz) dielectric relaxatio n as well as voltage fluctuations as a result of internal dynamic or s liding CDW in quasi one-dimensional chain compound (TaSe4)(2)I single crystals. The activation energy for normal conduction obtained from lo w field resistivity was Delta E = 0.122 +/- 0.004 eV. The most useful expression of dielectric relaxation for a strong damped system with on e degree of freedom is epsilon(omega) proportional to (1 + i omega tau (0))(-1), where relaxation times tau are distributed at the average ta u(0) .tau(0) versus 1/T shows thermal activation Delta E = 0.124 +/- 0 .004 eV. Voltage fluctuations produced by a sliding CDW are found to o riginate from random thermally activated transitions between metastabl e:states. Noise power spectra between 500 Hz and 600 kHz at temperatur es between 165 and 215 K have S(f) proportional to f(-alpha) dependenc e. The distribution of relaxation times and the temperature-dependent shortest relaxation time reflect CDW internal dynamics and the importa nce of free carriers on it.