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arXiv · 1902.00029

Antiferromagnetism and chiral d-wave superconductivity from an effective $t-J-D$ model for twisted bilayer graphene

Xingyu Gu·Chuan Chen·Jia Ning Leaw·Evan Laksono·Vitor M. Pereira·Giovanni Vignale·Shaffique Adam
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Abstract

Starting from the strong-coupling limit of an extended Hubbard model, we develop a spin-fermion theory to study the insulating phase and pairing symmetry of the superconducting phase in twisted bilayer graphene. Assuming that the insulating phase is an anti-ferromagnetic insulator, we show that fluctuations of the anti-ferromagnetic order in the conducting phase can mediate superconducting pairing. Using a self-consistent mean-field analysis, we find that the pairing wave function has a chiral d-wave symmetry. Consistent with this observation, we show explicitly the existence of chiral Majorana edge modes by diagonalizing our proposed Hamiltonian on a finite-sized system. These results establish twisted bilayer graphene as a promising platform to realize topological superconductivity.

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Xingyu Gu, Chuan Chen, Jia Ning Leaw, Evan Laksono, Vitor M. Pereira, Giovanni Vignale, Shaffique Adam. 2019-01-31. Antiferromagnetism and chiral d-wave superconductivity from an effective $t-J-D$ model for twisted bilayer graphene. https://doi.org/10.1103/physrevb.101.180506

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