30°Twisted Bilayer Graphene: Atomic Crystal Structure, Electronic Structure and Plasmonic Interactions

Recent discovery of unconventional superconductivity in twisted bilayer graphene (tBLG) has triggered intensive discussions about the importance of interlayer coupling effects in commensurate tBLG, which was overlooked previously. Much of its macroscale properties, such as conducting electron behavior and light matter interactions in the commensurate tBLG systems remain unknown. Here we present study of the interlayer coupling effects in the twisted 30° bilayer graphene system using surface sensitive low energy electron microscopy (LEEM), Raman scattering and infra-red scattering near-field optical microscopy (IR-sSNOM). Strong crystal structure coupling between two graphene sheets was revealed by a sharp 12-fold symmetrical LEED diffraction pattern. Enhancement of interlayer light scattering was also observed by Raman spectroscopy. Most surprisingly, the plasmonic interaction was observed to be sharply quenched on 30° twisted bilayer graphene in contrast with enhanced plasmonic interaction on non-twisted, bilayer graphene.