Flat band carrier confinement in magic angle twisted bilayer Graphene*

Magic angle twisted bilayer graphene has emerged as a powerful platform for studying strongly correlated electron physics, owing to its almost dispersionless low-energy, flat, bands and the ability to tune the band filling by electrostatic gating. Techniques to control the twist angle between graphene layers have led to rapid experimental progress but improving sample quality is essential for separating the delicate correlation physics from disorder effects. However, owing to the 2D nature of the system and the relatively low carrier density, the samples are highly susceptible to doping inhomogeneity which can drastically modify the local potential landscape. This potential disorder is distinct from the twist-angle variation which has been studied elsewhere. Using low temperature scanning tunneling spectroscopy we demonstrated that the flat bands in magic angle twisted bilayer graphene can substantially amplify even negligibly small doping inhomogeneity. As a result the charge carriers become confined, obscuring the correlation effects associated with the intrinsic physics of magic-angle twisted bilayer graphene