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

The magnetoluminescence spectra of symmetric quantum wells containing an electron gas show an abrupt transition from Landau level behavior (i.e. a linear shift of energy with field) to quadratic (exciton-like) behavior as the magnetic field is increased. This so-called “Mott transition” always occurs at the field at which the electron filling factor νe is 2, i.e. when the lowest Landau level is just filled. We show that the transition is a natural consequence of a hidden symmetry which has been shown to hold in two-dimensional 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”.