# Metal-insulator transition and dominant $d+id$ pairing symmetry in twisted bilayer graphene

## TL;DR

This study models twisted bilayer graphene using a two-orbital Hubbard model, revealing a metal-insulator transition, antiferromagnetic order, and dominant $d+id$ superconductivity, highlighting its tunability for correlated phenomena.

## Contribution

It provides a detailed theoretical analysis of the electronic phases and pairing symmetry in twisted bilayer graphene, emphasizing the role of electron correlations and interlayer coupling.

## Key findings

- Metal-insulator transition confirmed by temperature-dependent conductivity.
- Dominant $d+id$ superconducting pairing over a wide filling range.
- Suppression of conductivity, spin correlation, and superconductivity with increased interlayer coupling.

## Abstract

Motivated by recent experimental studies that have found signatures of a correlated insulator phase and tuning superconductivity in twisted bilayer graphene, we study the temperature-dependent conductivity, the spin correlation and the superconducting pairing correlation within a two-orbital Hubbard model on an emergent honeycomb lattice. The evaluation of the temperature dependence of the conductivity demonstrates that there is a metal-insulator transition, and the Mott phase at strong coupling is accompanied by antiferromagnetic order. The electronic correlation drives a $d+id$ superconducting pairing to be dominant over a wide filling region. All of the dc conductivity, the spin correlation and the superconductivity are suppressed as the interlayer coupling strength increases, and the critical $U_c$ for the metal-insulator transition is also reduced. Our intensive numerical results reveal that twisted bilayer graphene should be a uniquely tunable platform for exploring strongly correlated phenomena.