Hidden symmetry and the magnetically induced "Mott transition" in quantum wells containing an electron gas

The magnetoluminescence spectra of symmetric quantum wells containing an el ectron gas show an abrupt transition from Landau level behavior (i.e. a lin ear shift of energy with field) to quadratic (exciton-like) behavior as the magnetic field is increased. This so-called "Mott transition" always occur s at the field at which the electron filling factor nu(e) is 2, i.e, when t he lowest Landau level is just filled. We show that the transition is a nat ural consequence of a hidden symmetry which has been shown to hold in two-d imensional systems at high fields. The mechanism driving it has nothing to do with that driving the true Mott transition, and it would be better named a "symmetry-driven transition". (C) 2000 Elsevier Science Ltd. All rights reserved.