Phase diagram and orbital Chern insulator in twisted double bilayer graphene

Abstract

Compared with twisted bilayer graphene, twisted double bilayer graphene (TDBG) provides another important platform to realize the moiré flat bands. In this paper, we first calculate the valley Chern number phase diagram of TDBG in the parameter space spanned by the twist angle and the interlayer electric potential. To include the effects of interactions, we then phenomenologically introduce the spin-splitting and valley-splitting. We find that when the valley splitting is larger than the bandwidth of the first conduction band so that a gap is opened and the spin splitting is relatively weak, the orbital Chern insulator emerges at half-filling, associated with a large orbital magnetization (OM). Further calculations suggest that there is no sign reversal of the OM when the Fermi energy goes from the bottom to the top of the half-filling gap, as the OM remains negative in both AB-AB stacking and AB-BA stacking. The implications of our results for the ongoing experiments are also discussed.

12 pages, 9 figures

References in corpus (7)

• The electronic properties of graphene
• The electronic properties of bilayer graphene
• Topological confinement in bilayer graphene
• Orbital magnetization in periodic insulators
• Origin of band gaps in graphene on hexagonal boron nitride
• Flatbands in twisted double bilayer graphene
• Band structure and topological property of twisted double bilayer graphenes

Cited by in corpus (2)

• Tailoring the band structure of twisted double bilayer graphene with pressure
• High-Chern number phase in the topological insulator multilayer structures