Phase locking in charge-density-wave transport

Steps of constant current are observed in the dc I-V characteristic of charge-density-wave (CDW) systems subjected to combined ac and dc drives. The step widths are calculated by using a proposed form for the pinning potential, and by assuming phase locking between the applied ac drive and the CDW. Preliminary results indicate good qualitative and quantitative agreement with experiment for both harmonic and subharmonic steps in ${\mathrm{NbSe}}_3$.