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Phys. Rev. Lett. 100, 246806 (2008) [4 pages]

Quantum Hall Effect of Massless Dirac Fermions in a Vanishing Magnetic Field

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Kentaro Nomura1, Shinsei Ryu2, Mikito Koshino3,4, Christopher Mudry5, and Akira Furusaki6
1Department of Physics, Tohoku University, Sendai, 980-8578, Japan
2Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA
3Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
4Physics Department, Columbia University, New York, New York 10027, USA
5Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
6Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan

Received 20 January 2008; published 20 June 2008

The effect of strong long-range disorder on the quantization of the Hall conductivity σxy in graphene is studied numerically. It is shown that increasing Landau-level mixing progressively destroys all plateaus in σxy except the plateaus at σxy=∓e2/2h (per valley and per spin). The critical state at the Dirac point is robust to strong disorder and belongs to the universality class of the conventional plateau transitions in the integer quantum Hall effect. We propose that the breaking of time-reversal symmetry by ripples in graphene can realize this quantum critical point in a vanishing magnetic field.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.100.246806
DOI:
10.1103/PhysRevLett.100.246806
PACS:
73.43.−f, 72.10.−d, 73.21.−b, 73.50.Fq
 
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