Acoustoelectric Amplification in InSb

It was demonstrated by Kikuchi that two modes of acoustoelectric domain oscillation occur in InSb in a transverse magnetic field. Using lithium niobate transducers on an acoustic amplifier, we have measured linear acoustic gain as a function of electric and magnetic field and frequency. At high magnetic fields (B ≥ 3000 gauss) the results are in good agreement with White's theory. However, at low magnetic fields, the wavelength of the sound waves is less than the mean free path of the electrons, and the macroscopic theories break down. We have extended a microscopic theory of magnetacoustic interactions, due to Spector, to include electron drift. We find excellent agreement between theory and experiment over the whole range of magnetic field. Moreover, the results account very clearly for the two modes of acoustic domain formation.