A new phase from compression of carbon nanotubes with anisotropic Dirac fermions

Searching for novel functional carbon materials is an enduring topic of scientific investigations, due to its diversity of bonds, including sp-, sp(2)-, and sp(3)-hybridized bonds. Here we predict a new carbon allotrope, bct-C12 with the body-centered tetragonal I4/mcm symmetry, from the compression of carbon nanotubes. In particular, this structure behaviors as the Dirac fermions in the kz direction and the classic fermions in the k(x) and k(y) directions. This anisotropy originates from the interaction among zigzag chains, which is inherited from (n, n)-naotubes.