Electrostatic effects, band distortions and superconductivity in twisted graphene bilayers

TL;DR

This paper explores how electrostatic effects and band distortions in twisted bilayer graphene influence electron interactions and can promote superconductivity at specific electron fillings.

Contribution

It introduces a detailed analysis of electrostatic effects and band distortions in twisted bilayer graphene, revealing their role in enhancing electron interactions and superconductivity.

Findings

Charge modulation is significant away from neutrality.

Electrostatic potential distorts the low energy bands.

Band distortions lead to new local interactions that favor superconductivity.

Abstract

Bilayer graphene twisted by a small angle shows a significant charge modulation away from neutrality, as the charge in the narrow bands near the Dirac point is mostly localized in the regions of the Moir\'e pattern with $AA$ stacking. The resulting electrostatic potential gives rise to the dominant contribution to the electron-electron interaction within this low energy band, which becomes significantly distorted. The changes in the band structure are described by new local interactions, and lead to an assisted electron-hopping process. These couplings favor superconductivity at certain fillings.