Summary: he acoustoelectric effect is the manifestation of the transport of charge carriers in a
piezoelectric semiconductor by means of surface acoustic waves (SAWs). Lattice
Tdeformations induced by SAWs in a piezoelectric substrate generate potential waves
that can drag electrons along the wave propagation direction resulting in a net dc current or
voltage . This occurs even in an intrinsic medium, if electrons are fed into the device by
appropriate injector .
In one-dimensional (1D) devices, this effect gives rise to acoustoelectric current quantization
: control over the 1D-constriction width allows the accurate determination of the number
of electrons packed in each SAW-potential minimum down to single-electron transport. The
value of the current on the plateaus is I = nef, where e is the electron charge, f is the SAW
frequency, typically in the GHz range, and n is the number of electrons transferred through
the channel per SAW cycle.
The demonstration of quantized acoustoelectric effect led to the proposal of several
innovative devices. Indeed, the possibility of manipulating single electrons in 1D devices can
be exploited to implement scalable quantum-information-processing circuits with solid-state
devices. Additionally, converting the flux of individual SAW-driven electrons in a flux of
photons by injecting them into a two-dimensional hole gas, would realise an almost ideal
single-photon source for quantum-cryptography applications. At NEST we are exploring
these approaches aiming at the realisation of a solid-state Hadamard gate and a high-
repetition-rate single-photon source.