Enhanced interlayer coupling in twisted bilayer graphene quantum dots

Enhanced interlayer coupling occurs not only in the previously well-addressed AB stacking (Bernal structure), but also in the quasi-AA-stacking structures with a small and size-dependent twist angle. Although the interlayer interaction energy is dominated by Coulomb and van der Waals interaction, its twist-induced variation is mostly driven by the charge-transfer interaction. • Interlayer coupling strength in TBG QDs varies with twist angle. • Enhanced interaction may occur in both AB and AA stackings. • Electrostatic, vdW, polarization and CT contributions varies in different patterns. • Interaction energy is dominated by Coulomb and vdW interaction. • Interaction energy variation is dominated by the CT interaction. Interaction at the interface of two layers in twist bilayer graphene (TBG) and its quantum dots (QDs) is responsible for many of their intriguing properties. Using the block-localized wavefunctions (BLW) from first-principles calculations, the interlayer interaction and its evolution with twist angle are explored to address the driving forces that govern the interlayer coupling and decoupling. The interaction energy including its electrostatic, van der Waals (vdW), polarization and charge transfer (CT) contributions varies with twist angle but in different patterns. While the interaction energy is dominated by Coulomb and vdW interaction, its variation is dominated by the CT interaction. Moreover, interlayer coupling as strong as that in the full AB-stacking Bernal structure is characterized at a small and size-dependent angle from the full AA-stacking structure. The influence of interlayer stacking, atomic arrangement at the interface and cross-layer orbital overlap on interaction energy is discussed to address the twist-induced physics in TBG QDs. These findings not only deepen our understanding of the interlayer interaction nature of TBG QDs, but also suggest new approaches of optoelectronic modulation of graphene-based materials.