Broken flavor symmetries in rhombohedral multilayer graphene

Graphene multilayers have proven to be a rich platform to realize and control exotic emergent physics by engineering stacking arrangement, external fields, and proximity effects. Most observations of strong correlation effects in these systems are related to moiré flat bands, but recent experiments have demonstrated that even commensurately stacked graphene multilayers can feature a variety of strongly correlated phases, including superconductivity. These phases break spin and valley flavor symmetries. I will explain why the broken symmetry favored at large displacement fields in AB-bilayer and ABC-trilayer graphene is spontaneous valley coherence. This conclusion is based on a realistic lattice tight-binding description that faithfully captures inter-valley interactions, and a self-consistent Hartree-Fock mean field approximation for interaction. I will comment on the Fermi surface reconstructions and key electronic properties of the broken symmetry phase, and the relationship between superconductivity in ABC and AB bilayers and in magic-angle twisted bilayer graphene.