Combined Effects of Sound and Electric Fields upon the Conduction Electrons in Solids

The Boltzmann equation for the electronic distribution function in the presence of ultrasonic sound and a dc electric field is solved to produce a unified picture of the different effects resulting from the combined action of these two external disturbances. The response of the electronic system is described by the sum of various dc and ac current densities. Specifically it is shown which parts of the distribution function give rise to ultrasonic attenuation and to the acoustoelectric effect for both zero and nonzero external dc field. The Weinreich relation is found to be valid except for small correction terms due to collision drag. The orders of magnitude of the acoustoelectric field and the acoustoresistive effect are discussed for metals and semiconductors.