Article abstract
Nature Physics 3, 561 - 565 (2007)
Published online: 1 July 2007 | doi:10.1038/nphys658
Subject Category: Condensed-matter physics
Fractional quantum Hall effect in a quantum point contact at filling fraction 5/2
Jeffrey B. Miller1, Iuliana P. Radu2, Dominik M. Zumbühl2,3, Eli M. Levenson-Falk4, Marc A. Kastner2, Charles M. Marcus4, Loren N. Pfeiffer5 & Ken W. West5
Abstract
Recent theories suggest that the quasiparticles that populate certain quantum Hall states should exhibit exotic braiding statistics that could be used to build topological quantum gates. Confined systems that support such states at a filling fraction 
=5/2 are of particular interest for testing these predictions. Here, we report transport measurements of just such a system, which consists of a quantum point contact (QPC) in a two-dimensional GaAs/AlGaAs electron gas that itself exhibits a well-developed fractional quantum Hall effect at a bulk filling fraction bulk=5/2. We observe plateau-like features at an effective filling fraction of QPC=5/2 for lithographic contact widths of 1.2 
m and 0.8 m, but not 0.5 m. Transport near QPC=5/2 in the QPCs is consistent with a picture of chiral Luttinger-liquid edge states with inter-edge tunnelling, suggesting that an incompressible state at QPC=5/2 forms in this confined geometry.
- Division of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics and Astronomy, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Bell Labs, Lucent Technologies, Murray Hill, New Jersey 07974, USA
Correspondence to: Charles M. Marcus4 e-mail: marcus@harvard.edu
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