Generation of charge-density-wave conduction noise by moving phase vortices

A moving phase vortex at the end of a charge-density-wave conductor plays an essential role in the conversion of condensed carriers to free carriers. Under sliding conditions the periodic nucleation and destruction of these vortices generates the voltage oscillations (narrow-band noise) observed in these conductors. The role of free carriers in the noise generation is emphasized and the calculated ac voltage amplitude is compared with experiment. The exponential decay of the ac electric field away from the contact is determined by the phase-slip length which also determines the rigidity of the sliding current. A general discussion of the role of phase slips and dislocations in inhomogeneous geometries is given. Results from sample-length-dependence studies and thermal-gradient experiments are discussed. Competing theories for the noise based on interaction with random impurities are surveyed and their predictions compared with known experiments.