FREQUENCY AND VOLTAGE-DEPENDENCE OF THE COMPLEX SHEAR COMPLIANCE OF TAS3 - A RELAXATION ANALYSIS

We have measured the complex shear compliance of the charge-density-wa ve (CDW) conductor orthorhombic TaS3 for elastic frequencies between 0 .1 and 30 Hz, by directly measuring the sample strain (twist angle) fo r an applied alternating stress (torque). Both the real and imaginary parts of the compliance increase when the CDW is depinned. If the CDW is depinned with an ac current, the elastic anomalies depend on the fr equency of the current, as previously observed for the Young's modulus at higher frequencies. For dc depinning, we have fit the complex comp liance to a generalized Debye relaxation expression [S. Havriliak and S. Negami, J. Polym. Sci. C 14, 99 (1966)]. This fit allows us to dete rmine the voltage dependence of the relaxation strength and average re laxation time: tau similar to(V-V-T)(-3), where V-T is the threshold f or CDW depinning.