DIVERGING STRAINS IN THE PHASE-DEFORMATION MODEL OF SLIDING CHARGE-DENSITY WAVES

We show that when a spatially uniform, time-independent electric field is applied to a charge-density wave (CDW), the time-averaged local CDW velocity is spatially inhomogeneous, with nonzero spatial average, because models that do not allow for the coexistence of regions with different time-averaged mean velocities have places with infinite energy density. To establish this result we present a heuristic scaling argument, rigorous results on a simplified lattice model, and a study of the continuum phase equation of motion for the CDW. Flux-line motion in type-II superconductors is also considered; similarities and differences between flux-line motion and CDW motion are discussed.