Pulsed transport of electrons on liquid helium confined in narrow channels

We have used a Source-Gate-Drain configuration with electrons on liquid helium ( the Helium Field Effect Transistor "He-FET") to study the transport of "classical" electrons through narrow channels. The channels, formed by the split gate of the device, were between ten and a hundred mu m long and several mu m wide, and could be blocked completely by a negative bias voltage applied to the gate. In contrast to previous experiments, where the electron densities in source and drain were nearly the same and the system therefore was close to equilibrium, in the present measurement the drain was empty. The transport of the electrons through the channel was initiated by opening the gate with a short positive pulse with a duration down to nanoseconds, and the amount of electrons which passed during this time was registered. In this way, we could determine for the first time the transport properties of such a system on a nanosecond time scale and far off equilibrium. Measurements with varying gate voltage provide clear evidence for the formation of lanes of electrons in the channels.