Effects of CDW Motion on the Electric and Elastic Properties of (TaSe₄)₂I

Abstract

Electrical resistance, R, Young’s modulus, E and internal friction, Q⁻¹ in (TaSe₄)₂I were measured simultaneously as functions of temperature and dc-electric field strength, using a resonant flexural vibration technique. The CDW elasticity around the phase transition was investigated, and the predicted scaling relation was partly found. Change in R due to the CDW motion is always accompanied by change in E. In addition to the nonlinear conductivity just above the threshold dc-bias, V_T (9.5 mV(41 mV·cm⁻¹) at 250 K), a transient behavior was found below very low dc-bias, V₀(<0.25 mV at 250 K), and an increase in R, a strong decrease in E and an increase in Q⁻¹ were observed at high dc-bias (>0.3 V at 250 K). The former is attributed to the reversible atomic rearrangement in CDW domain walls, and the latter to some viscous motion of impurity atoms or lattice defects relative to neighboring chains. The temperature dependence of V_T between 120 K and 250 K was found to follow the relation, V_T∝exp (T₀⁄T), where T₀ is a constant.