# Ferromagnetic Mott State in Twisted Graphene Bilayers at the Magic Angle

## TL;DR

This paper investigates the Mott insulating state in twisted bilayer graphene at the magic angle, revealing a ferromagnetic insulator with distinct experimental signatures based on an effective spin model.

## Contribution

It derives an effective spin model for the ferromagnetic Mott state in twisted bilayer graphene, highlighting its exotic magnetic properties and experimental signatures.

## Key findings

- Identifies a ferromagnetic Mott insulator in twisted bilayer graphene.
- Derives an effective spin Hamiltonian from the tight-binding model.
- Predicts experimental signatures of the ferromagnetic Mott state.

## Abstract

We address the effective tight-binding Hamiltonian that describes the insulating Mott state of twisted graphene bilayers at a magic angle. In that configuration, twisted bilayers form a honeycomb superlattice of localized states, characterized by the appearance of flat bands with four-fold degeneracy. After calculating the maximally localized superlattice Wannier wavefunctions, we derive the effective spin model that describes the Mott state. We suggest that the system is an exotic ferromagnetic Mott insulator, with well defined experimental signatures.