Physics (Internal)

How to Understand the Magic of Twisted Bilayer Graphene

This event is part of the Biophysics/Condensed Matter Seminar Series.

Two layers of graphene rotated with respect to each other will form the twisted bilayer graphene (TBG). A year ago, Pablo Jarillo-Herrero’s group at MIT found that TBG at the so-called "magic angle" could become superconducting and insulating. Since then, more experimental data are accumulated. In this talk, I will try to understand how superconductivity and insulating phase emerge in TBG at magic angle. Through weak coupling approach, the so-called high-order van Hove singularity (VHS) is found near magic angle, which would lead to unconventional superconductivity and density wave phases in the presence of Coulomb repulsion. Through strong coupling approach, the Wannier orbitals are obtained for magic angle TBG, whose nontrivial shape induces the exotic effective tight-binding model and extended Hubbard model.