Electrically tunable flat bands with layer-resolved charge distribution in twisted monolayer-bilayer graphene

At a small twist angle, exotic electronic properties emerge in twisted monolayer-bilayer graphene (TMBG), including electrically switchable magnetic order and correlated insulating states. These fascinating many-body phenomena manifest when the low-energy bands feature a narrow bandwidth. In this study, we examine the electronic structure of TMBG using a tight-binding model with accurate parameters. Our results show that the low-energy bands of TMBG reach a minimum width at a quasi-magic angle, strongly correlated with the magic angle in twisted bilayer graphene. In addition, we find charge localization in the adjacent twisted layers and delocalization in the outer Bernal layer. Furthermore, in the presence of an electric field, an energy gap opens if lattice relaxation is taken into account. The particle-hole asymmetry in TMBG further leads to flatter conduction bands compared with the valence bands, with an electrically tunable band width and band gap.