Ferromagnetic Ground States in Twisted N-Layer Graphene

Magic angle twisted bilayer graphene exhibits a rich variety of correlated electronic phases, including the correlated insulator phase at integer fillings. Analytic calculations within the chiral limit indicate that certain Slater determinants with a non-zero charge gap can serve as exact many-body ground states for this phase. In a valleyless and spinless model at half filling, two distinct ferromagnetic Slater determinant states are identified as exact ground states. We investigate twisted N-layer graphene systems with an added layer symmetry, and define conditions where the ferromagnetic Slater determinants are the only Slater determinant ground states. Through analytical methods, we confirm that these conditions are met in twisted bilayer and equal twist angle trilayer graphene.