Complex evolution of the electronic structure from polycrystalline to monocrystalline graphene: generation of a new Dirac point

First calculations, employed to address the properties of polycrystalline graphene, indicate that the electronic structure of tilt grain boundaries in this system [1-4] displays a rather complex evolution towards graphene bulk, as the tilt angle decreases, with the generation of a new Dirac point at the Fermi level, and an anisotropic Dirac cone of low energy excitations. Moreover, the usual Dirac point at the {\bf K} point falls below the Fermi level, and rises towards it as the tilt angle decreases. Further, our calculations indicate that the grain-boundary formation energy behaves non-monotonically with the tilt angle, due to a change in the the spatial distribution and relative contributions of the bond-stretching and bond-bending deformations associated with the formation of the defect.\\[4pt] [1] L.~B.~Biedermann {\textit et al.}, Phys.~Rev.~B {\bf 79}, 125411 (2009). \\[0pt] [2] S.~S.~Datta {\textit et al.}, Nanoletters {\bf 9}, 7 (2009). \\[0pt] [3] P.~Simonis {\textit et al.}, Surf.~Sci. {\bf 511}, 319 (2002). \\[0pt] [4] G.~Gu {\textit et al.}, Appl.~Phys.~Lett. {\bf 90}, 253507 (2007).