Screening, nonadiabaticity, and quantized acoustoelectric current

Quantized single-electron transport driven by surface acoustic waves (SAW) through a pinched-off narrow constriction is studied theoretically. Long-ra nge Coulomb interaction causes the tunneling coupling between the two-dimen sional electron gas (2DEG) and the moving minimum of the SAW-induced potent ial to decay rapidly with time. The energy scale h/tau, associated with the characteristic time of this decay tau, controls both the width of the tran sition regions between the plateaus and the slope of the plateaus. This set s a limit for the accuracy of the quantization of acoustoelectric current a t lour temperature.