Correlated states in twisted trilayer graphene

Twisted bilayer graphene near the “magic angle” of 1.1 degrees can host low energy flat bands. Here we show tunable band hybridization and correlated states in twisted trilayer graphene, realized by placing monolayer graphene on top of a bernal bilayer graphene. Twisted monolayer-bilayer (tML-BL) devices were fabricated in a dual gate geometry allowing independent tunability of the carrier density and perpendicular displacement field D. For twist angle between 1.4 and 2 degrees the low energy band structure mostly preserves the monolayer and bilayer subbands, with an energy offset tunable with displacement field. At D = 0 the charge neutrality point is semi-metallic with compensated electrons and holes. Mapping the Landau levels as a function of density, D and magnetic field reveals transition between subbands, with a gapped monolayer subband. For twist angle ~ 1.2 degrees, we observed evidence of a flat band and emergent correlated insulating states, which are asymmetrically tunable with displacement field due to the lack of mirror symmetry.