Surface acoustic wave driven quantized current transport

The piezoelectric potential of a surface acoustic wave (SAW) can drive carriers in a semiconductor device over macroscopic distances. An application where optically generated electron-hole pairs are separated, transported and deliberately recombined was demonstrated a few years ago [Phys. Rev. Lett. 78 (1997) 4099]. Also around that time it was shown that the longitudinal confinement provided by the potential minima of a SAW travelling along a one-dimensional channel may combine with the lateral channel confinement to form moving quantum dots with a well defined number n of electrons in each dot [J. Phys.: Condens. Matter 8 (1996) L531]. This gives rise to a quantized current I = n (.) e (.) f. This dynamic version of the Single Electron Tunneling operates at GHz frequencies and delivers currents in the nA range. The obvious application of the effect is in basic metrology, where it would enable the so called 'Electrical Triangle' experiment which combines Josephson effect, quantum Hall effect and a quantized current to check the relation (h/2e(2)) (.) e = h/2e self consistently. This paper reviews the experimental work on SAW driven currents and in detail the work done at the PTB, Germany, and NPL, UK, as well as suggested applications in other areas like single-photon generation [Phys. Rev. A 58 (1998) R2680], quantized charge pumping through carbon nanotubes [Phys. Rev. Lett. 87 (2001) 276802] or quantum computing [Phys. Rev. B 62 (2000) 8410]. (C) 2004 Published by Elsevier B.V.