# Electrically controllable magnetism in twisted bilayer graphene

## TL;DR

This paper demonstrates that twisted bilayer graphene exhibits electrically controllable magnetic states, including antiferromagnetic and ferromagnetic phases, with complex spiral magnetic order emerging without spin-orbit coupling, offering new insights into 2D frustrated magnetism.

## Contribution

It reveals how electrical bias induces diverse magnetic phases and spiral order in twisted bilayer graphene, a phenomenon not previously reported in this material.

## Key findings

- Bias controls AF and F magnetic polarization.
- Spiral magnetic order emerges without spin-orbit coupling.
- Magnetism is tunable and competes with lattice-antiferromagnetic instability.

## Abstract

Twisted graphene bilayers develop highly localised states around AA-stacked regions for small twist angles. We show that interaction effects may induce either an antiferromagnetic (AF) and a ferromagnetic (F) polarization of said regions, depending on the electrical bias between layers. Remarkably, F-polarised AA regions under bias develop spiral magnetic ordering, with a relative $120^\circ$ misalignment between neighbouring regions due to a frustrated antiferromagnetic exchange. This remarkable spiral magnetism emerges naturally without the need of spin-orbit coupling, and competes with the more conventional lattice-antiferromagnetic instability, which interestingly develops at smaller bias under weaker interactions than in monolayer graphene, due to Fermi velocity suppression. This rich and electrically controllable magnetism could turn twisted bilayer graphene into an ideal system to study frustrated magnetism in two dimensions, with interesting potential also for a range of applications.