Strong Correlations and d+id Superconductivity in Twisted Bilayer Graphene

TL;DR

This paper investigates the phase diagram of twisted bilayer graphene near the magic angle, revealing a crossover between d+id superconductivity and Mott insulating behavior driven by electron correlations, consistent with experimental observations.

Contribution

It provides a comprehensive phase diagram using advanced many-body techniques, highlighting the interplay of superconductivity and insulating phases in twisted bilayer graphene.

Findings

Identification of a crossover between d+id superconductivity and Mott insulator near half-filling.

Confirmation of experimental results regarding correlated phases in twisted bilayer graphene.

Use of unbiased renormalization group methods to analyze strongly correlated phenomena.

Abstract

We compute the phase diagram of twisted bilayer graphene near the magic angle where the occurrence of flat bands enhances the effects of electron-electron interactions and thus unleashes strongly-correlated phenomena. Most importantly, we find a crossover between d+id superconductivity and Mott insulating behavior near half-filling of the lowest electron band when the temperature is increased. This is consistent with recent experiments. Our results are obtained using unbiased many-body renormalization group techniques combined with a mean-field analysis of the effective couplings.