Magic-angle twisted bilayer graphene (TBG) hosts a multitude of correlated insulating, superconducting, and topological phases. We show that adding an insulating monolayer of WSe2 to the TBG stabilizes superconductivity down to angles as small as 0.79º. At angles in this range, both the correlated insulating states and the band gaps between flat and dispersive bands disappear, leading to metallic bands across the accessible range of electron density. We additionally observe weak antilocalization and the breaking of the fourfold spin-valley symmetry usually observed in TBG, consistent with strong spin-orbit coupling. The results constrain theoretical explanations for the superconductivity and correlated insulators while emphasizing the importance of the dielectric environment for engineering the correlated states in moiré systems.

Robert Polski

California Institute of Technology