Electron pairing instability in magic angle twisted bilayer graphene*

Superconductivity is one of the most intriguing properties observed recently in magic angle twisted bilayer graphene. Its origin is evidently closely tied to the nearly flat low energy bands at magic angle, which possess both spin/valley flavor symmetries and unique topological properties. The precise mechanism of pairing remains unclear however. Here we make an unbiased assessment of different pairing models, taking both Coulomb interactions and effective interactions induced by electron-phonon coupling into account. We find that It is essential to account for the screening of Coulomb interactions by remote metallic gates which increase the momentum dependence of Coulomb interactions and open the door to unconventional pairing channels. I will also comment on orbital suppression of superconductivity by an in-plane magnetic field, and on the possibility of using the magnetic-field dependence of superconductivity to identify the pairing mechanism.