title: Observation of an intrinsic bandgap and Landau level renormalization in graphene/boron-nitride heterostructures.
abstract: Van der Waals heterostructures formed by assembling different two-dimensional atomic crystals into stacks can lead to many new phenomena and device functionalities. In particular, graphene/boron-nitride heterostructures have emerged as a very promising system for band engineering of graphene. However, the intrinsic value and origin of the bandgap in such heterostructures remain unresolved. Here we report the observation of an intrinsic bandgap in epitaxial graphene/boron-nitride heterostructures with zero crystallographic alignment angle. Magneto-optical spectroscopy provides a direct probe of the Landau level transitions in this system and reveals a bandgap of ~38 meV (440 K). Moreover, the Landau level transitions are characterized by effective Fermi velocities with a critical dependence on specific transitions and magnetic field. These findings highlight the important role of many-body interactions in determining the fundamental properties of graphene heterostructures.
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA.
authors.forename: Zhi-Guo
authors.initials: ZG
authors.lastname: Chen
authors.affiliation: Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Zhiwen
authors.initials: Z
authors.lastname: Shi
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Lu
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA.
authors.forename: You
authors.initials: Y
authors.lastname: Lai
authors.affiliation: IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors.forename: Hugen
authors.initials: H
authors.lastname: Yan
authors.affiliation: 1] Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA [2] Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Zhang
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Li