Hidden symmetry and magnetospectroscopy of quantum wells near filling factor v = 2

Abstract

he magnetoluminescence spectra of symmetric quantum wells containing an electron gas show an abrupt changeover from Landau-level behavior (i.e., linear shift of energy with magnetic field) to quadratic (excitonlike) behavior as the field is increased. This so-called "Mott transition" occurs when the electron filling factor v(e) is 2, i.e., when the lowest Landau level is just filled. We show that the changeover is a natural consequence of the hidden symmetry that has been shown to hold in two-dimensional systems at high fields. This symmetry is broken when the integer parts of v(e)/2 and V-h//2 differ (v(h), the hole filling factor, is very small in these experiments), This symmetry breaking can also account for the new emission bands that are observed in such spectra when v(e) becomes larger than 2, and these bands can be described, at least qualitatively, in the framework of the magnetoexciton theory. These bands include the red-shifted magnetoplasmon and shake-up satellites and the blue-shifted cyclotron satellites. We also discuss the possible existence of a new type of trion (chargcd exciton), associated with the electron n(e) = 1 Landau level, and conclude that these trions should be observable.