Electron Localization in a Two-Dimensional System in Strong Magnetic Fields. III. Impurity-Concentration Dependence and Level-Mixing Effects

Abstract

A computer simulation is performed to study localization in a two-dimensional electron system in strong magnetic fields. When scatterers only with attractive potentials are present and their concentration is not so high, the density of states is not symmetric around the center of each Landau level. The energy of delocalized states in this case is shown to be close to the energy where the real part of Green’s function vanishes except in the case of extremely low concentrations of scatterers. Effects of mixings between different Landau levels are also studied by including a finite number of Landau levels. It is shown that extended states remain to be present even if level mixings are important and that the energy for extended states is shifted to the higher energy side with the decrease of the strength of the magnetic field.