ACOUSTOELECTRIC EFFECTS IN QUANTUM CONSTRICTIONS

A dc current induced in a quantum constriction by a traveling acoustic wave (or by nonequilibrium ballistic phonons) is considered. We show that in many important situations the effect is originated from acoust ically induced scattering between the propagating and reflecting state s in the constriction. Two particular regimes corresponding to relativ ely high and low acoustic frequencies are discussed. In the first regi me, the acoustoelectric effect in a smooth constriction can be underst ood by semiclassical considerations based on local conservation laws. For the low-frequency regime, we show that the acoustoconductance is c losely related to the zero-field conductance. The qualitative consider ations are confirmed by numerical calculations both for smooth and abr upt channels.