Coexistence of multiple dirac nodal points and nodal lines in two-dimensional carbon nanotube arrays

Abstract

Seeking for novel fermions in two-dimensional (2D) materials is of practical significance for devices with extraordinary transport properties. In this work, 2D carbon nanotube arrays (CNTAs) formed by ‘fusible’ connection of uniform CNTs are studied based on first-principles calculations. We find the coexistence of multiple Dirac points and diverse nodal lines (including type I, type II, and type III in band crossing modes, and both open and closed in forms) formed by four entangled bands near the Fermi levels. Such kind of coexistence, which can be regarded as the splitting of eight-fold degeneracy or double Dirac nodal lines, is the results of the interaction between the upper and lower surfaces of CNTAs, and leads to the nontrivial arc-like, drumhead-like, and torus edge states in their nanoribbons concurrently. Our study suggests that CNTAs can be excellent platforms to study the entanglements between different states, and excellent candidates for quantum devices.