Symmetry-breaking Transitions and Superconductivity in Magic-Angle Graphene Multilayers

Graphene moiré superlattice systems have emerged as a platform hosting an abundance of correlated insulating, topological, and superconducting phases. However, so far, only alternating twisted stacking geometries of bilayer and trilayer graphene are found to exhibit robust superconductivity exhibiting Fraunhofer patterns and zero resistance. Here we investigate strongly correlated phases and superconductivity in magic-angle twisted graphene tri-, quadri-, and pentalayers placed in proximity to a tungsten diselenide (WSe₂) monolayer. All three multilayer structures exhibit flavor symmetry-breaking cascade of electronic transitions, superconductivity, and, surprisingly, insulating states in the trilayer and quadrilayer. Moreover, we identify universal and layer-specific features in this family of moiré structures arising from the intricate relations between superconducting states, symmetry-breaking transitions, and van Hove singularities. Unexpectedly, as the number of layers is increased, superconductivity is observed in an increasingly larger range of filling factors. Our results highlight the non-trivial role of dispersive bands in defining properties of highly tunable graphene moiré superconductors.

 

Acknowledgement: This work has been primarily supported by the Department of Energy DOE-QIS program (DE-SC0019166) and in part by Office of Naval Research (grant no. N142112635) and Sloan foundation (grant no. FG-2020-13716).