Levitation of the quantum Hall extended states in the B→0 limit -: art. no. 165301

We investigate the fate of the quantum Hall extended states within a continuum model with spatially correlated disorder potentials. The model can be projected onto a couple of the lowest Landau bands. Levitation of the n=0 critical states is observed if at least the two lowest Landau bands are considered. The dependence on the magnetic length l(B)=((h) over bar/(eB))(1/2) and on the correlation length of the disorder potential eta is combined into a single dimensionless parameter (eta) over cap=eta/l(B). This enables us to study the behavior of the critical states for vanishing magnetic field. In the two Landau band limit, we find a disorder dependent saturation of the critical states' levitation which is in contrast to earlier propositions, but in accord with some experiments.