Gate tunable topological phase transitions in superlattice potential modulated bilayer graphene

Superlattice potential modulation combined with a displacement field produces flat bands in bilayer graphene [1], some of which have nonzero valley-projected Chern numbers. In this talk I will show that at integer fillings of the topological flat bands, phase transitions between quantum anomalous Hall, valley Hall, and trivial insulator states can be driven by tuning displacement field and the shape and strength of the superlattice potential. The topologically trivial flat bands are localized in space and display Hubbard model physics. I will present mean-field phase diagrams in the parameter space of displacement field and superlattice potential strength at various filling factors. Finally, I will discuss the similarities and differences between the correlated insulating states in superlattice potential modulated bilayer graphene and those in magic-angle twisted bilayer graphene and transition metal dichalcogenide heterobilayers.

[1] S.A.A. Ghorashi, et al. arXiv:2206.13501.