Cascade of superconducting domes and magnetic order in charge neutral and ¼ filled magic angle bilayer graphene

Superconductivity often occurs close to symmetry broken parent states, in particular when doping magnetically ordered states. Flat bands in Moiré lattices in twisted bilayer graphene have emerged as a rich and highly tunable model platform, where superconducting domes were found close to correlated insulating states at ± ½ band filling, raising speculations of an unconventional pairing mechanism. Here we report on the fabrication of highly twist-angle homogeneous devices, which allow to resolve correlated states at all integer fillings ± ¼, ± ½, ± ¾ of the four-fold spin and valley degenerate Moiré band, and a gapped insulating state at charge neutrality. We find an enhanced critical temperature of ~ 3 K of the superconducting dome close to – ½ filling, and strikingly we observe three new superconducting domes at much lower temperatures, when slightly doping the charge neutral point and the ±¼ filled correlated states. Interestingly, the weakly pronounced – ¼ correlated state shows a sharp hysteretic resistance enhancement when a perpendicular magnetic field above 3.6 tesla is applied, consistent with a field stabilized magnetically ordered state.
Overall, our study shows that symmetry broken and superconducting states occur not only around half-filling, but are common across the entire Moiré band, including charge neutrality. The co-existence of superconductivity and magnetic order in the – ¼ correlated states points towards a possible pairing mechanism.