Researchers from ETH Zurich and Aalto University showed that sandwiching two slightly rotated layers of graphene between a ferromagnetic insulator provides a unique setting for new electronic states.

A valley-spiral in magnetically encapsulated twisted bilayer graphene (Aalto University)

The combination of ferromagnets, graphene's twist engineering, and relativistic effects force the "valley" property to dominate the electrons behavior in the material. In particular, the researchers showed how these valley-only states can be tuned electrically, providing a materials platform in which valley-only states can be generated.