Quantum Hall states near the charge-neutral Dirac point in graphene.
We investigate the quantum Hall (QH) states near the charge-neutral Dirac point of a high mobility graphene sample in high magnetic fields. We find that the QH states at filling factors nu=+/-1 depend only on the perpendicular component of the field with respect to the graphene plane, indicating that they are not spin related. A nonlinear magnetic field dependence of the activation energy gap at filling factor nu=1 suggests a many-body origin. We therefore propose that the nu=0 and +/-1 states arise from the lifting of the spin and sublattice degeneracy of the n=0 Landau level, respectively.
Jiang
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Department of Physics, Columbia University, New York, New York 10027, USA. jiang@magnet.fsu.edu
Zhang
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Stormer
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Kim
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