Nonlinear Conductivity and Broad Band Noise of Monoclinic TaS₃

Abstract

We have studied the nonlinear conductivity and the accompanied broad band noise of monoclinic TaS₃. The noise voltage becomes maximum just above the threshold field E_T of the nonlinear conduction. For comparison, the same measurements were made for NbSe₃ and the similar results were obtained. The generation of broad band noise is explained in terms of two valued process, and the number of degrees of freedom of the CDW motion, N, is estimated to be 10⁹⁻¹⁰/cm³ in both of monoclinic TaS₃ which is semiconducting at low temperatures, and NbSe₃ which is metallic. This result indicates that the motion of the CDW’s is not described as that of a rigid body. N is found to decrease with decreasing temperature in monoclinic TaS₃.