Transport and relaxation properties in low-dimensional (TaSe 4 ) 2 J crystals

Abstract

Charge density wave (CDW) occurs in low-dimensional solids as a consequence of Peierls Transition. Various field and frequency-dependent effects as well as of excess noise are related to CDW transport. Low frequency (in the range of 10 - 10<SUP>6</SUP> Hz) dielectric relaxation as well as voltage fluctuations as a result of internal dynamic or sliding CDW in quasi one- dimensional chain compound (TaSe<SUB>4</SUB>)<SUB>2</SUB>J single crystals were investigated. The activation energy for normal conduction obtained from low field resistivity was (Delta) E equals 0.122 plus or minus 0.004 eV. The most useful expression of dielectric relaxation for strong damped system with one degree of freedom is (epsilon) ((omega) )varies direct as(1 plus i(omega) (tau) <SUB>0</SUB>)<SUP>-1</SUP>degree where relaxation times (tau) are distributed at average (tau) <SUB>0</SUB> . (tau) <SUB>0</SUB> vs 1/T shows thermal activation (Delta) E equals 0.124 plus or minus 0.004 eV. Voltage fluctuations produced by a sliding CDW are found to originate from random thermally activated transitions between metastable states. Noise power spectra between 500 Hz and 600 kHz at temperatures from 165 to 215 K have S(f)varies direct asf<SUP>-a</SUP> dependence. Distribution of relaxation times and temperature- dependent shortest relaxation time reflect CDW internal dynamics and importance of free carriers on it.