The narrow-band noise (NBN) in the charge-density-wave conductor ${\mathrm{NbSe}}_3$ is found to fluctuate dynamically in frequency, amplitude, and harmonic content. The NBN width is dominated by slow frequency fluctuations rather than a spatial velocity distribution. Mode locking quenches these fluctuations yielding a dramatic narrowing of the NBN; but amplitude fluctuations remain. The NBN width also scales with the broad-band noise amplitude. These results demonstrate the crucial importance of temporal incoherence in the sliding charge-density-wave condensate and particularly on mode locking.

• Received 21 May 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.1849