Phenomenology of current oscillations by sliding charge density waves

Bardeen's suggestion that the dc current associated with the sliding of a charge density wave instead of the dc electric field determines the dynamics of the phase, is formulated in a simple but self-consistent way. The resulting equation of motion for the phase reduces to that of the classical model of a rigid charge density wave far above threshold with a new, nondissipative scaling frequency. It is suggested that the harmonic content of the narrow band noise monitored as function of dc bias may decide between both interpretations. The model may also have relevance to the observation of subharmonics and chaos in charge density wave systems.