Increase of quantum Hall plateau width by electron-phonon interaction

We perform model calculations which illustrate the role of electron-phonon interaction in the integer quantum Hall effect. We show that electron-phono n interaction can generate electron velocities which contribute to the form ation of the quantized plateaus of sigma(xy). In systems which contain insu lating states (typical quantum Hall samples) the fraction of this kind of v elocities is small. This leads to slightly larger plateaus of sigma(xy) com pared to those of the dissipative conductivity. Experimentally, this differ ence has been known for a long time, but remained unexplained so far. In th e special case where the substrate potential has no spatial fluctuations in the direction of the macroscopic electric field, all states are conducting and the dissipative conductivity vanishes only close to the band edges. Ne vertheless, the calculated Hall conductivity shows surprisingly broad quant ized plateaus, which hers ape entirely generated by electron-phonon interac tion. Our results show that dissipation must not necessarily vanish in the Hall plateau regime, contrary to a widespread belief. (C) 1999 Elsevier Sci ence B.V. All rights reserved.