We perform transport measurements in high quality bilayer graphene pnp junctions with suspended top gates. At a magnetic field B=0, we demonstrate band gap opening by an applied perpendicular electric field, with an On/Off ratio up to 20,000 at 260mK. Within the band gap, the conductance decreases exponentially by 3 orders of magnitude with increasing electric field, and can be accounted for by variable range hopping with a gate-tunable density of states, effective mass, and localization length. At large B, we observe quantum Hall conductance with fractional values, which arise from equilibration of edge states between differentially-doped regions, and the presence of an insulating state at filling factor {\nu}=0. Our work underscores the importance of bilayer graphene for both fundamental interest and technological applications.
@article{arxiv.1009.4669,
title = {Quantum Transport and Field Induced Insulating States in Bilayer Graphene pnp Junctions},
author = {Lei Jing and Jairo Velasco and Philip Kratz and Gang Liu and Wenzhong Bao and Marc Bockrath and Chun Ning Lau},
journal= {arXiv preprint arXiv:1009.4669},
year = {2015}
}
Comments
4 figures, to appear in Nano Lett. Minor typos corrected