Twisted bilayer graphene (TBG) near the magic angle (~1.1°) has been established to be a highly tunable platform that hosts correlated insulating and superconducting phases. However, the relation between these states remains elusive, owing to their sensitivity to microscopic details. Here we show that adding an insulating WSe2 monolayer to the TBG stabilizes superconductivity at twist angles much smaller than the magic angle. For the smallest twist angle of 0.79˚, superconductivity is still robust despite the metallic behavior across the whole electron density range. Our results demonstrate the impact of the dielectric environment on correlated phases in TBG and put strict constraints for the theoretical explanation of superconductivity in this system.

Yiran Zhang

California Institute of Technology