R N BHATT and XIN WAN*

Department of Electrical Engineering, Princeton University, Princeton, NJ 08544-5263, USA

* Present address: National High Magnetic Field Laboratory, Florida State University, Tallahassee,
FL 32310, USA

Abstract.

We report results of a study of (integer) quantum Hall transitions in a single or multiple Landau levels for non-interacting electrons in disordered two-dimensional systems, obtained by projecting a tight-binding Hamiltonian to the corresponding magnetic subbands. In finite-size systems, we find that mesoscopic effects often dominate, leading to apparent non-universal scaling behavior in higher Landau levels. This is because localization length, which grows exponentially with Landau level index, exceeds the system sizes amenable to the numerical study at present.   When band mixing between multiple Landau levels is present, mesoscopic effects cause a crossover from a sequence of quantum Hall transitions for weak disorder to classical behavior for strong disorder. This behavior may be of relevance to experimentally observed transitions between quantum Hall states and the insulating phase at low magnetic fields.

Keywords:  Mesoscopic effects; quantum Hall transitions; finite-size scaling.

Pacs Nos.  73.43.Cd; 73.43.Nq;71.30.+h