Complete charge density-wave mode locking and freeze-out of fluctuations inNbSe3

We report the observation of complete rf-induced mode locking in the charge-density-wave (CDW) state of ${\mathrm{NbSe}}_3$. Over each mode-locked region, the CDW phase velocity is uniquely determined by the frequency of the rf field, and all broadband noise normally associated with CDW conduction is absent. These observations demonstrate that broadband CDW conduction noise is not a necessary consequence of CDW motion. We suggest that, in the mode-locked state, random-phase velocity fluctuations are frozen out through a macroscopic synchronization of CDW domains.