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Evidence for a spontaneous gapped state in ultraclean bilayer graphene.

ABSTRACT: At the charge neutrality point, bilayer graphene (BLG) is strongly susceptible to electronic interactions and is expected to undergo a phase transition to a state with spontaneously broken symmetries. By systematically investigating a large number of single-and double-gated BLG devices, we observe a bimodal distribution of minimum conductivities at the charge neutrality point. Although ?(min) is often approximately 2-3 e(2)/h (where e is the electron charge and h is Planck's constant), it is several orders of magnitude smaller in BLG devices that have both high mobility and low extrinsic doping. The insulating state in the latter samples appears below a transition temperature T(c) of approximately 5 K and has a T = 0 energy gap of approximately 3 meV. Transitions between these different states can be tuned by adjusting disorder or carrier density.

SUBMITTER: Bao W

PROVIDER: S-EPMC3390874 | biostudies-other | 2012 Jul

REPOSITORIES: biostudies-other

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Evidence for a spontaneous gapped state in ultraclean bilayer graphene.

Bao Wenzhong W Velasco Jairo J Zhang Fan F Jing Lei L Standley Brian B Smirnov Dmitry D Bockrath Marc M MacDonald Allan H AH MacDonald Allan H AH Lau Chun Ning CN

Proceedings of the National Academy of Sciences of the United States of America 20120608 27

At the charge neutrality point, bilayer graphene (BLG) is strongly susceptible to electronic interactions and is expected to undergo a phase transition to a state with spontaneously broken symmetries. By systematically investigating a large number of single-and double-gated BLG devices, we observe a bimodal distribution of minimum conductivities at the charge neutrality point. Although σ(min) is often approximately 2-3 e(2)/h (where e is the electron charge and h is Planck's constant), it is sev ...[more]

PMID: 22685212

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