A. Veligura, H. J. van Elferen, N. Tombros, J. C. Maan, U. Zeitler, B. J. van Wees
We report a change of three orders of magnitudes in the resistance of a
suspended bilayer graphene flake which varies from a few k{\Omega}s in the high
carrier density regime to several M{\Omega}s around the charge neutrality point
(CNP). The corresponding transport gap is 8 meV at 0.3 K. The sequence of
appearing quantum Hall plateaus at filling factor \nu=2 followed by \nu=1
suggests that the observed gap is caused by the symmetry breaking of the lowest
Landau level. Investigation of the gap in a tilted magnetic field shows that
the resistance at the CNP decreases linearly with the total magnetic field.
Those observations are in agreement with a spontaneous valley splitting at zero
magnetic field followed by Zeeman splitting of the spins originating from
different valleys with increasing magnetic field. Although the exact cause of
the valley splitting is still debatable, the above picture suggests the
manifestation of the anomalous quantum Hall ground state in the bilayer
graphene sample.
View original:
http://arxiv.org/abs/1202.1753
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