Magnetic density gap in the quantum Hall regime

In conventional AlGaAs/GaAs heterostructures, there is a residual quantum Hall effect in the limit of quenched disorder. This residual effect is due to the existence of a magnetic density gap (MDG) which arises in the Fermi level transition between two Landau levels. Self-consistent calculation of the electronic properties of the two-dimensional system taking into account Zeeman splitting and the Ando-Uemura exchange energy shows that the MDG is strongly dependent on the filling factor as well as on temperature and barrier capacitance. It also reveals a strong enhancement of the g*-factor in agreement with the data of Usher et al. Phys. Rev. B, 41, 1129 (1990).