The electronic spectra of rotationally faulted graphene bilayers are
calculated using a continuum formulation for small fault angles that identifies
two distinct electronic states of the coupled system. The low energy spectra of
one state features a Fermi velocity reduction which ultimately leads to
pairwise annihilation and regeneration of its low energy Dirac nodes. The
physics in the complementary state is controlled by pseudospin selection rules
that prevent a Fermi velocity renormalization and produce second generation
symmetry-protected Dirac singularities in the spectrum. These results are
compared with previous theoretical analyses and with experimental data.Comment: 5 pages, 3 figure
