We report a change of three orders of magnitudes in the resistance of a suspended bilayer graphene flake which varies from a few kΩs in the high carrier density regime to several MΩs 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 ν=2 followed by ν=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 indicates that the resistance at the CNP shows a weak linear decrease for increasing total magnetic field. Those observations are in agreement with a spontaneous valley splitting at zero magnetic field followed by splitting of the spins originating from different valleys with increasing magnetic field. Both, the transport gap and B field response point toward spin polarized layer antiferromagnetic state as a ground state in the bilayer graphene sample. The observed non-trivial dependence of the gap value on the normal component of B suggests possible exchange mechanisms in the system.
@article{arxiv.1202.1753,
title = {Transport Gap in Suspended Bilayer Graphene at Zero Magnetic Field},
author = {A. Veligura and H. J. van Elferen and N. Tombros and J. C. Maan and U. Zeitler and B. J. van Wees},
journal= {arXiv preprint arXiv:1202.1753},
year = {2012}
}