Band-unfolding approach to Moir\`e-induced band-gap opening and   Fermi-level-velocity reduction in twisted bilayer graphene
  We report on the energy spectrum of electrons in twisted bilayer graphene (tBLG) obtained by the band-unfolding method in the tight-binding model. We find the band-gap opening at particular points in the reciprocal space, that elucidates the drastic reduction of the Fermi-level velocity with the tiny twisted angles in tBLGs. We find that Moir\`e pattern caused by the twist of the two graphene layers generates interactions among Dirac cones, otherwise absent, and the resultant cone-cone interactions peculiar to each point in the reciprocal space causes the energy gap and thus reduced the Fermi-level velocity. 
Hirofumi Nishi, Yu-ichiro Matsushita, Atsushi Oshiyama
cond-mat.mtrl-sci