Mele, Eugene J2023-05-232023-05-232010-04-122010-11-04https://repository.upenn.edu/handle/20.500.14332/42806The low-energy electronic spectra of rotationally faulted graphene bilayers are studied using a longwavelength theory applicable to general commensurate fault angles. Lattice commensuration requires lowenergy electronic coherence across a fault and pre-empts massless Dirac behavior near the neutrality point. Sublattice exchange symmetry distinguishes two families of commensurate faults that have distinct low-energy spectra which can be interpreted as energy-renormalized forms of the spectra for the limiting Bernal and AA stacked structures. Sublattice-symmetric faults are generically fully gapped systems due to a pseudospin-orbit coupling appearing in their effective low-energy Hamiltonians.Physical Sciences and MathematicsPhysicsArticle