Nematic superconductivity in magic-angle twisted bilayer graphene from atomistic modeling

Twisted bilayer graphene (TBG) develops large moire patterns at small twist angles with flat energy bands hosting domes of superconductivity. The large system size and intricate band structure have however hampered investigations into the superconducting state. Here, using full-scale atomistic modelling with local electronic interactions, we find at and above experimentally relevant temperatures a highly inhomogeneous superconducting state with nematic ordering on both atomic and moire length scales. The nematic state has a locally anisotropic real-valued d-wave pairing, with a nematic vector winding throughout the moire pattern, and is three-fold degenerate. Although d-wave symmetric, the superconducting state has a full energy gap, which we tie to a pi-phase interlayer coupling. The superconducting nematicity is further directly detectable in the local density of states. Our results show that atomistic modeling is essential and also that very similar local interactions produce very different superconducting states in TBG and the high-temperature cuprate superconductors.

Automated summary

By using atomistic modeling and local electronic interactions, this study investigates twisted bilayer graphene (TBG) and reveals the formation of large moire patterns and flat energy bands that host superconductivity at small twist angles. It also identifies the existence of highly inhomogeneous and nematic superconducting state with both atomic and moire length scale ordering.