Role of acoustical reflections in quantised acousto-electric current devices

In surface acoustic wave devices exhibiting quantised acoustoelectric current (QAC) transport, the precision of quantisation, which is crucial in a potential application as a current standard, is influenced by reflections of the acoustic wave. We studied the role of these reflections in two extreme limits: an intentionally applied counterpropagating SAW beam simulates intense reflections, whereas a nearly reflectionless situation is realised with a specially designed device. In contrast to previous findings, we conclude that acoustic echoes are always detrimental and should be avoided completely.