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 degrees-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 angstrom, revealing an expansion of 0.17 angstrom as compared with that of Bernalstacked bilayer graphene. This result provides important insights for elucidating the origin of the magnitude of coupling between graphene layers.