Unexpected features of branched flow through high-mobility two-dimensional electron gases

Abstract

GaAs-based two-dimensional electron gases (2DEGs) show a wealth of remarkable electronic states1,2,3, and serve as the basis for fast transistors, research on electrons in nanostructures4,5 and prototypes of quantum-computing schemes6. All of these uses depend on the extremely low levels of disorder in GaAs 2DEGs, with low-temperature mean free paths ranging from micrometres to hundreds of micrometres7. Here we study how disorder affects the spatial structure of electron transport by imaging electron flow in three different GaAs/AlGaAs 2DEGs, whose mobilities range over an order of magnitude. As expected, electrons flow along narrow branches that we find remain straight over a distance roughly proportional to the mean free path. We also observe two unanticipated phenomena in high-mobility samples. In our highest-mobility sample we observe an almost complete absence of sharp impurity or defect scattering, indicated by the complete suppression of quantum coherent interference fringes. Also, branched flow through the chaotic potential of a high-mobility sample remains stable to significant changes to the initial conditions of injected electrons.

Cite this article

Jura, M., Topinka, M., Urban, L. et al. Unexpected features of branched flow through high-mobility two-dimensional electron gases. Nature Phys 3, 841–845 (2007). https://doi.org/10.1038/nphys756

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