Classical dynamics of electrons in quantized-acoustoelectric-current devices

Abstract

We present a numerical study of the classical dynamics of interacting spinless electrons in quantized-acoustoelectric-current devices. In these devices, a surface acoustic wave (SAW) captures electrons from a two-dimensional electron gas (2DEG) and transports a fraction of them through a narrow depleted constriction. If the same number of electrons are transported in each cycle, a quantized current will result. In our model, each SAW minimum captures $\ensuremath{\sim}30$ electrons as the SAW maximum behind it passes through the 2DEG chemical potential. It then moves toward the center of the constriction losing on average one electron every 3 ps as it becomes smaller. For temperatures below $\ensuremath{\sim}1.7\mathrm{K}$ the electrons form a crystal, which heats up to this temperature through the equipartition of excess potential energy produced by the loss of electrons. Thermal excitation out of the minima then results in variations in the number of electrons transported. At temperatures above $\ensuremath{\sim}1.7\mathrm{K}$ the electrons are in a more liquidlike state and evaporative cooling occurs. The dependence of acoustoelectric current on the constriction potential and the temperature are found to be in good agreement with experiment.