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

Abstract

Twisted bilayer graphene (TBG) develops large moiré 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 moiré length scales. The nematic state has a locally anisotropic real-valued d-wave pairing, with a nematic vector winding throughout the moiré pattern, and is three-fold degenerate. Although d-wave symmetric, the superconducting state has a full energy gap, which we tie to a π-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.

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• Theory of Topological Superconductivity and Antiferromagnetic Correlated Insulators in Twisted Bilayer WSe${}_2$
• Robust and tunable coreless vortices and fractional vortices in chiral $d$-wave superconductors
• Intrinsic non-magnetic ${\varphi }_0$ Josephson junctions in twisted bilayer graphene
• Defect-induced band restructuring and length scales in twisted bilayer graphene
• Atomistic theory of moiré Hofstadter's butterfly in magic-angle graphene
• Enhanced chiral edge currents and orbital magnetic moment in chiral $d$-wave superconductors from mesoscopic finite-size effects
• Superconductivity from spin fluctuations and long-range interactions in magic-angle twisted bilayer graphene
• Nodal Nematic Superconductivity in Multiple-Flat-Band Land
• Coexistence of nematic superconductivity and spin density wave in magic-angle twisted bilayer graphene
• Buckling and flat bands in twisted bilayer graphene