Charge pumping in driven electron ratchets

A sample structure that uses off-center, interdigitated gates to induce a DC current in a two-dimensional electron gas, driven by two phase shifted AC voltages, applied to the finger gates is discussed. We find that the current as a function of the phase shift resembles the waveform of the driving voltage. This can be explained using a transport model, based on local currents, which are given by Ohmʹs and Kirchhoffʹs laws. Despite its simplicity, the model is able to explain nearly all experimental observations, including the dependence of the pumping current on phase shift, waveform, frequency, and amplitude.