Broad-Band 1/ f Noise and Nonlinear Conductivity in an Insulating Charge Density Wave System at Low Electric Fields

We have performed noise measurements in the Charge Density Wave system Rb 0.3 MoO 3 below the threshold at low temperature. In this regime this system nearly behaves as an insulator, it presents a very small and strongly nonlinear conductivity (10 -15 to 10 -12 Ω -1 ). We have observed a 1/ f current noise through the sample, which increases dramatically with the amplitude of the electric field and whose amplitude slowly decreases with time. We have found that a direct relationship exists between this Broad-Band Noise amplitude and the d.c. conductivity, independently of the time of observation. These results are attributed to fluctuating CDW domains. From the relationship, it is possible to evaluate the number of independent fluctuating CDW domains contributing to the noise. Surprisingly this number is independent of E and of the history of the sample.