Quantized current in one-dimensional channel induced by surface acoustic waves

Abstract

We report an observation of the quantized acoustoelectric current induced by surface acoustic wave with frequency f≈3 GHz through a 1D channel defined in a GaAs–AlGaAs heterostructure by a split gate. When the split gate is pinched off the acoustoelectric current can be observed only for sufficiently high RF power levels, consistent with electrons being forced through the channel by the surface acoustic wave. As gate voltage is made less negative the current shows quantized steps in units I= e· f where e is the electron charge. The current on the first plateau coincides with the calculated value I= e· f with the accuracy limited by the error (0.3%) of our measuring instrument. The current value at the plateau was found to be stable over an interval of source-drain voltages and temperatures up to 4 K. The observed quantization is due to trapping of electrons in the moving potential minima, with the number of electrons in each minimum controlled by electron–electron repulsion. The accuracy of the current quantization observed in our experiments suggests that SAW devices may open a new route towards the creation of a current standard. Different possible designs of SAW based current standard are discussed.