Spectroscopy of Correlation-enabled Chern Insulators in Magic-Angle Twisted Bilayer Graphene*

Electronic interactions play a central role for the formation of various correlated phases in magic-angle twisted bilayer graphene (MATBG). Here we report results on local properties of newly discovered correlated Chern insulating phases that develop in the presence of finite magnetic fields. We identify Chern numbers of these topological phases using a novel spectroscopic technique hinging on scanning tunneling microscopy (STM) that enables us to reconstruct a local, spatially dependent, Landau fan diagram. The corresponding spectroscopy in finite fields directly reveals that these Chern phases arise from the strong exchange-like interaction that acts on the Hofstadter sub-bands. Moreover, the spatial mapping in an area where twist angle slowly changes further reveals that these phases form in fields B<8T only in close vicinity (0.1deg) of the magic-angle value. Our results highlight the importance of strong interactions in the formation of topological phases in MATBG.