Remnant pockets of carriers left over after formation of a charge density wave (CDW) were brought to a current-carrying quantum Hall state. The generated Hall voltage polarizes and puts to sliding the flexible CDW background. The screening from the CDW allows for a so strong redistribution of normal electrons density that an integer Hall state is reached at one edge at the expense of the full depletion at another edge of the Hall bar. The regime of exactly compensated collective and normal counter-currents develops in the open-circuit direction across the bar. The annihilation of currents proceeds via a sequence of phase slips - the space-time vortices of the CDW phase - leading to the high (~GHz) frequency spontaneous generation. The internally generated frequency was detected by Shapiro steps quantized in voltage increments like for superconductors. This picture results from experiments on micron-sized Hall bars in crystals of NbSe3, prepared by the technique of focused ion beams. The interpretation is confirmed and illustrated by numerical solution of the derived equations describing the nonlinear spatio-temporal effects.

%solution of the derived equations describing the nonlinear spatio-temporal effects.