Electronic structure and its tuning of large-angle twisted monolayer–bilayer graphene

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Twisted monolayer–bilayer graphene (tMBG) has recently been demonstrated to be an attractive moiré system due to the presence of wide magic angles and unique topological flatbands. However, despite the considerable attention devoted to the magic-angle (small-angle) region, the electronic properties of tMBG with large twist angles have rarely been explored so far. Here, we investigate the electronic structure of large-angle (1.8°–7.8°) tMBG by using scanning tunneling microscopy and spectroscopy. We observed moiré superlattice-induced van Hove singularities, as well as low- and high-energy band singularities in the tunneling spectroscopy, which exhibit obvious twist angle and spatial dependence. Based on these spectroscopic characteristics, the detailed band structure information of large-angle tMBG is revealed, including the interlayer coupling strengths of both the twisted and Bernal-stacked interfaces, by combining with continuum model calculations. Crucially, we demonstrate that the electronic structure of tMBG can be effectively modulated through multi-interface coupling engineering, i.e., by selectively tuning the twisted-interface coupling via local corrugation and simultaneously tuning both the twisted and Bernal-stacked interface couplings through external adsorption. Our work reveals the angle-dependent fundamental electronic properties of tMBG and puts forward a multi-interface coupling strategy for designing multilayer moiré materials.