van der Waals heterostructures combining graphene and hexagonal boron nitride

As the first in a large family of 2D van der Waals (vdW) materials, graphene has attracted enormous attention owing to its remarkable properties. The recent development of simple experimental techniques for combining graphene with other atomically thin vdW crystals to form heterostructures has enabled the exploration of the properties of these so-called vdW heterostructures. Hexagonal boron nitride is the second most popular vdW material after graphene, owing to the new physics and device properties of vdW heterostructures combining the two. Hexagonal boron nitride can act as a featureless dielectric substrate for graphene, enabling devices with ultralow disorder that allow access to the intrinsic physics of graphene, such as the integer and fractional quantum Hall effects. Additionally, under certain circumstances, hexagonal boron nitride can modify the optical and electronic properties of graphene in new ways, inducing the appearance of secondary Dirac points or driving new plasmonic states. Integrating other vdW materials into these heterostructures and tuning their new degrees of freedom, such as the relative rotation between crystals and their interlayer spacing, provide a path for engineering and manipulating nearly limitless new physics and device properties. This is an overview of the new physics that emerges in van der Waals heterostructures consisting of graphene and hexagonal boron nitride, including the integer and fractional quantum Hall effects, novel plasmonic states and the effects of emergent moire superlattices. Key pointsAtomically thin flakes of van der Waals materials such as graphene and hexagonal boron nitride (hBN) can be mixed and matched into heterostructures with fundamentally new optoelectronic properties.Graphene encapsulated in hBN has very high mobility, with very low charge carrier inhomogeneity and ballistic transport characteristics over micrometre length scales at low temperature.High-mobility graphene devices exhibit well-developed multicomponent integer and fractional quantum Hall effects, as well as additional exotic correlated electronic phases in a magnetic field.When the graphene and hBN crystals are rotationally aligned, a long-wavelength moire superlattice emerges, which creates new, finite-energy Dirac points in the graphene bandstructure and leads to the Hofstadter butterfly spectrum.Graphene-hBN heterostructures host new hybrid polaritons, as well as plasmonic excitations with exceptionally long lifetimes that can be tuned with a moire superlattice.