Hidden symmetry and magnetospectroscopy of quantum wells near filling factor nu=2 - art. no. 045305

The magnetoluminescence spectra of symmetric quantum wells containing an el ectron gas show an abrupt changeover from Landau-level behavior (i.e., line ar shift of energy with magnetic field) to quadratic (excitonlike) behavior as the field is increased. This so-called "Mott transition" occurs when th e 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 hi dden symmetry that has been shown to hold in two-dimensional systems at hig h 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 experiment s), 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 ba nds can be described, at least qualitatively, in the framework of the magne toexciton theory. These bands include the red-shifted magnetoplasmon and sh ake-up satellites and the blue-shifted cyclotron satellites. We also discus s the possible existence of a new type of trion (chargcd exciton), associat ed with the electron n(e) = 1 Landau level, and conclude that these trions should be observable.