Sodium-terminated zigzag graphene nanoribbon: A one-dimensional   semimetal with a tilted Dirac cone
  Using first principles pseudopotential density functional theory calculations, we find that terminating zigzag graphene nanoribbons (ZGNR) with monovalent alkali atoms at a reduced concentration has a dramatic impact on their properties. In particular, using sodium atoms for the saturation of ZGNR edges at half the concentration of edge-carbon atoms make it a one dimensional, perfect semimetal, where the valance and conduction bands meet at only a single, Dirac-like point. Unlike pristine graphene, the Dirac-"cones" of Na-ZGNR is not symmetric with respect to wave vector, but rather it is tilted. 
Ozan Ar{\i}, \.Ibrahim Dursun, and R. Tu\u{g}rul Senger
cond-mat.mes-hall