Bistability of non-linear conductivity in insulators with sliding charge density waves.

At low temperatures in semiconducting compounds with a sliding charge density wave (CDW), it is shown that the nonlinear d. c current voltage characteristic should be bistable. The high velocity branch describes free sliding of the CDW, motion which becomes undamped at zero temperature ("Frohlich superconductivity"). In the low-velocity branch the CDW is highly deformed, with a velocity low enough that backflow currents of thermally excited quasiparticles can screen the local electric fields produced by the moving CDW. The results are compared with recent experiments on the blue bronze K sub (0.3) MoO sub 3.