Topological nodal lines in three-dimensional single wall carbon nanotube network

Topological semimetals, including Dirac, Weyl, node-line, triply degenerate semimetal and so on, receive a great deal of attention due to their interesting topological nature and intriguing physical phenomena. In present work, we find that the band crossing topological node-line semimetal states can be realized in a three-dimensional (3,3) single wall carbon nanotube ((3,3) SWCNT) network when spin-orbit coupling (SOC) of C atom is ignored. Detailed symmetry and effective model analysis reveal that time-reversal (T) and space inversion (P) symmetries, as well as mirror symmetries in the system are the origin of the topological node-line in the system. Unexpectedly, the nodal lines are contained in a kind of nodal surface around the Gamma originated from accidental band degeneracy. The topological nodal lines and trivial nodal surface in the carbon nanotube network will deepen our understanding of the formation of the nodal line semimetal states.