Phonon interactions with magnetically quantized two-dimensional carrier systems: the integer and fractional quantum Hall states

Abstract

This chapter describes investigations of the interaction of phonons with magnetically quantized two-dimensional (2-D) electron systems including the quantum Hall states, with particular attention to work using acoustic phonons as probes. This includes studies of phonon emission from the two diagonally opposite ‘hot spots’ of a Hall bar where the current enters and leaves. One study detected the phonons using bolometers placed opposite the corners and, in another, the temperature increases at the ‘hot spots’ were indicated by the thickness of superfluid helium film covering the Hall bar. Information has also been obtained on the frequency spectrum of the emitted phonons. Studies have been made of the location and frequency dependence of the absorption of phonons in the integer states. Phonon absorption studies of the fractional quantum Hall state provide support for the magnetoroton picture, and the fruitful studies of the quantum Hall states using surface acoustic waves are reviewed in detail.