J. Velasco Jr., Y. Lee, Z. Zhao, Lei Jing, P. Kratz, Marc Bockrath, C. N. Lau
Landau level gaps are important parameters for understanding electronic interactions and symmetry-broken processes in bilayer graphene (BLG). Here we present transport spectroscopy measurements of LL gaps in double-gated suspended BLG with high mobilities in the quantum Hall regime. By using bias as a spectroscopic tool, we measure the gap {\Delta} for the quantum Hall (QH) state at filling factor {\nu}=4, -2 and -1. {\Delta} of {\nu}=4 scales linearly with magnetic field B and is independent of the out-of-plane electric field E_perp. {\Delta} of {\nu}=-2 and {\Delta}{\nu}=-1 also scale linearly with B, but are strongly E_perp-dependent -- upon application of E_perp, the gap sizes increase by an order of magnitude. Our studies provide the first measurements of the gaps of the broken symmetry QH states in BLG with well-controlled E_perp, and suggest that there are at least 2 distinct QH states at {\nu}=2, stabilized by electric and magnetic fields, respectively.
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http://arxiv.org/abs/1303.3649
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