title: Angle-resolved Raman imaging of interlayer rotations and interactions in twisted bilayer graphene.
abstract: Few-layer graphene is a prototypical layered material, whose properties are determined by the relative orientations and interactions between layers. Exciting electrical and optical phenomena have been observed for the special case of Bernal-stacked few-layer graphene, but structure-property correlations in graphene which deviates from this structure are not well understood. Here, we combine two direct imaging techniques, dark-field transmission electron microscopy (DF-TEM) and widefield Raman imaging, to establish a robust, one-to-one correlation between twist angle and Raman intensity in twisted bilayer graphene (tBLG). The Raman G band intensity is strongly enhanced due to a previously unreported singularity in the joint density of states of tBLG, whose energy is exclusively a function of twist angle and whose optical transition strength is governed by interlayer interactions, enabling direct optical imaging of these parameters. Furthermore, our findings suggest future potential for novel optical and optoelectronic tBLG devices with angle-dependent, tunable characteristics.
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States.
authors.forename: Robin W
authors.initials: RW
authors.lastname: Havener
authors.forename: Houlong
authors.initials: H
authors.lastname: Zhuang
authors.forename: Lola
authors.initials: L
authors.lastname: Brown
authors.forename: Richard G
authors.initials: RG
authors.lastname: Hennig
authors.forename: Jiwoong
authors.initials: J
authors.lastname: Park
mesh_terms: D006108:Graphite / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012399:Rotation; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D006108:Graphite