Anharmonicity and asymmetry of Landau levels for a two-dimensional electron gas

TL;DR

This paper investigates how anharmonicity and asymmetry in Landau levels affect the density of states in a two-dimensional electron gas at a heterojunction, considering impurity effects and their impact on quantum Hall transport.

Contribution

It introduces a detailed calculation of the density of states with enhanced disorder potential, revealing asymmetries and impurity band formations under magnetic fields.

Findings

Impurity bands form at high magnetic fields for both attractive and repulsive potentials.

Asymmetry in the density of states influences quantum Hall transport properties.

Band tails or impurity bands appear at low magnetic fields depending on impurity type.

Abstract

We calculate the density of states of a two dimensional electron gas located at the interface of a GaAlAs/GaAs heterojunction. The disorder potential which is generally created by a single doping layer behind a spacer, is here enhanced by the presence of a second delta doped layer of scatterers which can be repulsive or attractive impurities. We have calculated the density of states by means of the Klauder's approximation, in the presence of a magnetic field of arbitrary strength. At low field either band tails or impurity bands are observed for attractive potentials, depending on the impurity concentration. At higher field, impurity bands are observed for both repulsive and attractive potentials. We discuss the effect of such an asymmetrical density of states on the transport properties in the quantum Hall effect regime.