Abstract
Recent experiments in graphene heterostructures have observed Chern insulators - integer and fractional Quantum Hall states made possible by a periodic substrate potential. Here we study theoretically the competition between different Chern insulators, which can be tuned by the amplitude of the periodic potential, leads to a new family of quantum critical points described by QED₃-Chern-Simons theory. At these critical points, N_f flavors of Dirac fermions interact through an emergent U(1) gauge theory at Chern-Simons level K, and remarkably, the entire family (with any N_f or K) can be realized at special values of the external magnetic field. Transitions between particle-hole conjugate Jain states realize "pure" QED₃ in which multiple flavors of Dirac fermion interact with a Maxwell U(1) gauge field. The multi-flavor nature of the critical point leads to an emergent SU(N_f) symmetry. Specifically, at the transition from a ν=1/3 to 2/3 quantum Hall state, the emergent SU(3) symmetry predicts an octet of charge density waves with enhanced susceptibilities, which is verified by DMRG numerical simulations on microscopic models applicable to graphene heterostructures. We propose experiments on Chern insulators that could resolve open questions in the study of 2+1 dimensional conformal field theories and test recent duality inspired conjectures.