To achieve a steady-state collective current due to the CDW sliding, current must be injected at one electrode and extracted at the other. Equivalently, CDW phase fronts must be added at one electrode and removed at the other. In the region of the sample between the contacts, the CDW phase fronts are moving when the CDW is sliding. In the regions of the sample which are outside the electrical contacts, there is no collective current and the CDW phase fronts are stationary. Schematic illustration of the experimental configuration.
Normal current is injected and extracted from the current electrodes.
CDW or collective mode conduction takes place only in the region between the current electrodes. The mechanism which converts normal current to collective current at the electrodes is straightforward. Before the electric field is applied, the CDW is uniform. As the electric field is applied, phase fronts in between the electrodes try to move down, dilating the CDW near the electrode on the top. The goal of the present experiments is to measure the time dependence of this strain field as the sign of the electric field is reversed.