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. The unusual electronic properties of graphene can be modified by placing it on a boron-nitride substrate with a small crystallographic alignment angle. Chen et al.now reveal that such heterostructures grown by epitaxy have a large bandgap, useful for applications using magneto-optical spectroscopy.