The nature of localization in graphene under quantum Hall conditions

Abstract

Particle localization is an essential ingredient in quantum Hall physics. In conventional high-mobility two-dimensional electron systems such as in GaAs/AlGaAs semiconductor heterostructures, Coulomb interactions were shown to compete with disorder and to have a central role in particle localization. Here, we address the nature of localization in graphene where the carrier mobility, quantifying the disorder, is two to four orders of magnitude smaller than in GaAs two-dimensional electron systems. We image the electronic density of states and the localized state spectrum of a graphene flake in the quantum Hall regime with a scanning single-electron transistor. Our microscopic approach provides direct insight into the nature of localization. Surprisingly, despite strong disorder, our findings indicate that localization in graphene is not dominated by single-particle physics, but rather by a competition between the underlying disorder potential and the repulsive Coulomb interaction responsible for screening. The effect of disorder in conventional two-dimensional electron systems is usually described in terms of individual electrons interacting with an underlying disorder potential. Scanning single-electron transistor measurements of graphene in a strong magnetic field indicate that in this system, coulombic interactions between electrons must also be taken into account.

Cite this article

Martin, J., Akerman, N., Ulbricht, G. et al. The nature of localization in graphene under quantum Hall conditions. Nature Phys 5, 669–674 (2009). https://doi.org/10.1038/nphys1344

View full text

>> Full Text:   The nature of localization in graphene under quantum Hall conditions