Impact of the Angular Alignment on the Crystal Field and Intrinsic Doping of Bilayer Graphene/BN Heterostructures

The energy gap of Bernal-stacked bilayer graphene can be tuned by applying a perpendicular electric field. The origin of this gap can be traced down to the breaking of its inversion symmetry by an onsite potential difference between the layers. This degree of tunability makes bilayer graphene a perfect playground for the study of the effects of electric fields, such as the crystalline field, which are developed when layers of other materials are deposited on top of it. Here, we introduce a novel device architecture allowing a simultaneous control over the applied displacement field and the crystalline alignment between two materials. Our experimental and numerical results confirm that the crystal field and electrostatic doping due to the interface reflect the 120 deg symmetry of the bilayer graphene/BN heterostructure and are highly affected by the commensurate state. These results provide an unique insight into the role of the twist angle in the development of internal crystal fields and intrinsic electrostatic doping in heterostructures. Our results highligth the importance of layer alignment, beyond the existence of a moiré superlattice, to understand and simulate the intrinsic properties of a van der Waal heterostructure.