Atomic arrangements of quasicrystal bilayer graphene: Interlayer distance expansion

Bilayer graphene exhibits outstanding characteristics that can be modified by adjusting the twist angle between two layers. An exact 30^∘-twisted bilayer graphene forms a material comprising two-dimensional quasicrystals accompanied by a relativistic Dirac fermion. In this study, the atomic arrangements of quasicrystal bilayer graphene on a SiC(0001) substrate are identified using positron diffraction. The interlayer distance in quasicrystal bilayer graphene is determined to be 3.46 {}, revealing an expansion of 0.17 {} as compared with that of Bernal-stacked bilayer graphene. This result provides important insights for elucidating the origin of the magnitude of coupling between graphene layers.