Sliding charge-density waves as rough growth surfaces

Using high-resolution x-ray scattering techniques we have measured the tran sverse structure of the sliding charge-density wave (CDW:I in NbSe3. For te mperatures between 70 K and 120 K and for applied currents up to 40x the th reshold current for sliding, the scattering peak for the sliding CDW is sig nificantly broader than that for the pinned CDW, indicating that the slidin g state is less correlated than the pinned state. Using scaling analysis, w e show that the CDW phase roughness exponent alpha rises from 0.60 +/- 0.01 in the pinned state to 0.80 +/- 0.01 in the sliding: state.