Topology and Correlations in Magic Angle Bilayer Graphene

The recent discovery of superconductivity and Mott insulators in twisted bilayer graphene and related materials points to the importance of correlation effects. An additional interesting and potentially crucial ingredient is band topology inherited from the Dirac fermion dispersion of graphene. We will discuss our theoretical efforts to derive faithful tight binding models that captures both the symmetry and topology of the flat bands, as well as their energetics. We then discuss aspects of the Mott and superconducting phases and find that key aspects of the physics differ from previously studied correlated superconductors.

1. arXiv:1803.09742: Origin of Mott insulating behavior and superconductivity in twisted bilayer graphene
Hoi Chun Po, Liujun Zou, Ashvin Vishwanath, T. Senthil

2. arXiv:1806.07873: Band Structure of Twisted Bilayer Graphene: Emergent Symmetries, Commensurate Approximants and Wannier Obstructions
Liujun Zou, Hoi Chun Po, Ashvin Vishwanath, T. Senthil

3. arXiv:1808.02482: Faithful Tight-binding Models and Fragile Topology of Magic-angle Bilayer Graphene
Hoi Chun Po, Liujun Zou, T. Senthil, Ashvin Vishwanath

4. arXiv:1805.06867: Superconductivity from Valley Fluctuations and Approximate SO(4) Symmetry in a Weak Coupling Theory of Twisted Bilayer Graphene
Yi-Zhuang You, Ashvin Vishwanath