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

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Bilayer graphene with small internal twist angles develops large scale moiré patterns with flat energy bands hosting both correlated insulating states and superconductivity. The large system size and intricate band structure have however hampered investigations into the properties of the superconducting state. Here, we use full-scale atomistic modeling with local electronic interactions and find a highly inhomogeneous superconducting state with nematic ordering on both the atomic and moiré lattice length scales. More specifically, we obtain locally anisotropic real-valued d-wave pairing with a nematic vector winding throughout the moiré pattern, generating a three-fold ground state degeneracy. Despite the d-wave nature, the superconducting state has a full energy gap, which we further tie to a π-phase interlayer coupling. The superconducting nematicity is easily detected through signatures in the local density of states. Our results show not only that atomistic modeling is essential for twisted bilayer graphene but also that the superconducting state is necessarily distinctly different from that of the high-temperature cuprate superconductors, despite similarity in electronic interactions.

Schmidt, JohannUppsala universitet,Materialteori(Swepub:uu)johsc827 (författare)
Parhizgar, FariborzUppsala universitet,Materialteori(Swepub:uu)farpa529 (författare)
Black-Schaffer, Annica M.Uppsala universitet,Materialteori(Swepub:uu)annsc679 (författare)
Uppsala universitetMaterialteori (creator_code:org_t)

Av författaren/redakt...: Löthman, Tomas; Schmidt, Johann; Parhizgar, Farib ...; Black-Schaffer, ...

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