THE ROLE OF CONTACTS IN THE GENERATION OF CHARGE-DENSITY-WAVE-CONDUCTICN NOISE(EXPERIMENTS ON MX_3 COMPOUNDS, International Symposium on NONLINEAR TRANSPORT AND RELATED PHENOMENA IN INORGANIC QUASI ONE DIMENSIONAL CONDUCTORS)

Abstract

Experiments have been performed to investigate the physical origin of the narrow band noise which accompanies charge density wave conduction in the trichalcogenides MX_3. In one experiment we show by current shunting that silver paint contacts seriously perturb the non-Ohmic current. The sample is segmented into parts which oscillate independently. The amplitude relation between frequency components from different parts of the sample suggests that the origin of the noise is at the contacts. In a series of experiments on nine samples we find that the ac voltage of the noise is independent of the length of the sample. This confirms that the noise is due to a fluctuating voltage at the contacts rather than a bulk ac current. We discuss these results in terms of phase slip at the sample ends and describe the role of phase vortices (dislocations) in noise generation.