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Nature 462, 196-199 (12 November 2009) | doi:10.1038/nature08582; Received 17 August 2009; Accepted 14 October 2009; Published online 1 November 2009

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Observation of the fractional quantum Hall effect in graphene

Kirill I. Bolotin1,3,4, Fereshte Ghahari1,3, Michael D. Shulman2, Horst L. Stormer1,2 & Philip Kim1,2

  1. Department of Physics,
  2. Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
  3. These authors contributed equally to this work.
  4. Present address: Department of Physics, Vanderbilt University, Nashville, Tennessee 37235, USA.

Correspondence to: Philip Kim1,2 Correspondence and requests for materials should be addressed to P.K. (Email: pk2015@columbia.edu).

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When electrons are confined in two dimensions and subject to strong magnetic fields, the Coulomb interactions between them can become very strong, leading to the formation of correlated states of matter, such as the fractional quantum Hall liquid1, 2. In this strong quantum regime, electrons and magnetic flux quanta bind to form complex composite quasiparticles with fractional electronic charge; these are manifest in transport measurements of the Hall conductivity as rational fractions of the elementary conductance quantum. The experimental discovery of an anomalous integer quantum Hall effect in graphene has enabled the study of a correlated two-dimensional electronic system, in which the interacting electrons behave like massless chiral fermions3, 4. However, owing to the prevailing disorder, graphene has so far exhibited only weak signatures of correlated electron phenomena5, 6, despite intense experimental and theoretical efforts7, 8, 9, 10, 11, 12, 13, 14. Here we report the observation of the fractional quantum Hall effect in ultraclean, suspended graphene. In addition, we show that at low carrier density graphene becomes an insulator with a magnetic-field-tunable energy gap. These newly discovered quantum states offer the opportunity to study correlated Dirac fermions in graphene in the presence of large magnetic fields.

  1. Department of Physics,
  2. Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
  3. These authors contributed equally to this work.
  4. Present address: Department of Physics, Vanderbilt University, Nashville, Tennessee 37235, USA.

Correspondence to: Philip Kim1,2 Correspondence and requests for materials should be addressed to P.K. (Email: pk2015@columbia.edu).