Charge-density-wave transport in quasi-one-dimensional conductors. I. Current oscillations

We present a detailed experimental study of current oscillation phenomena in charge-density-wave (CDW) transport. The amplitude and harmonic content of the quasiperiodic component of the current oscillations remain large and approximately constant even at very high electric fields, suggesting that the form and magnitude of the impurity pinning potential are approximately independent of applied field. A simple single-coordinate model of CDW motion in a nonsinusoidal pinning potential, motivated by the quantum tunneling theory of CDW depinning, accounts for all the qualitative features of our results. Nearly perfect velocity coherence seems to be characteristic of weak-impurity-pinned CDWs in high-quality NbSe3. However, other types of crystal defects together with contact effects act to broaden the observed distribution of CDW velocities. This velocity distribution plays a crucial role in the ringing observed in the CDW response to a current pulse, and also in generating the broadband noise.