Suppression of broadband noise at mode locking in driven vortex matter

We measure voltage noise generated by current-driven vortices for fields corresponding to the solid phase when at equilibrium including the peak-effect regime, focusing on a change in broadband noise (BBN) as the vortex system undergoes a mode-locking (ML) resonance. For all the fields steplike structure indicative of ML is observed in the I-V curves. We find that BBN at high frequencies (but well below the ac drive frequency) is suppressed inside the ML steps. The results are consistent with the view that the mode-locked state is a frozen solid pinned in the moving frame of reference.