New nanoporous graphyne monolayer as nodal line semimetal: Double Dirac points with an ultrahigh Fermi velocity

Abstract

Two-dimensional (2D) carbon materials play an important role in nanomaterials. We propose a new carbon monolayer, named hexagonal-4,4,4-graphyne (H 4,4,4 -graphyne), which is a nanoporous structure composed of rectangular carbon rings and triple bonds of carbon. Using first-principles calculations, we systematically studied the structure, stability, and band structure of this new material.We found that its energy is much lower than that of some experimental carbon materials and it is stable at least up to 1500 K. In contrast to the single Dirac point band structure of other 2D carbon monolayers, the band structure of H 4,4,4 -graphyne exhibits double Dirac points along the high symmetry points and the corresponding Fermi velocities (1.04~1.27 × 10 6 m/s) are asymmetric and higher than that of graphene. The origin of these double Dirac points is traced back to the nodal line states, which can be well explained by a tight-binding model. The H 4,4,4 -graphyne forms a moiré superstructure when placed on top of a BN substrate, while keeping the double Dirac points. These properties make H 4,4,4 -graphyne a promising semimetal material for applications in high-speed electronic devices.

Dirac Semimetal Protected by Nonsymmorphic Mirror Symmetries in TPH‐Graphene

“…Due to the bonding flexibility of carbon atoms, numerous 2D carbon allotropes have been proposed theoretically. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] These carbon allotropes exhibit some amazing properties, such as ultrahigh ideal strength, [9] high electron mobility at room temperature, [8] superconductivity, [22] good catalytic activity, [23] ferromagnetism, [24] and negative Poisson's ratio. [9,25] It is no doubt that the fascinating properties will encourage further investigations of these 2D carbon materials.…”

Computational discovery of spin-polarized semimetals in spinel materials

“…Interestingly, the nodal line can be twisted into a number of shapes, resulting in more complicated topological phases such as nodal chain, Hopf-link states, and nodal-net. [14][15][16][17] Topological semimetals have already been identified in a series of materials, including IrF 4 , [18] Ba 3 Si 4 , [19] carbon network, [14] and β-cristobalite BiO 2 [20]. The majority of them, however, are nonmagnetic, whereas magnetic semimetals appear to exhibit exotic features such as tunable nodal points and anomalous Hall effect.…”

“…Due to its various applications, the ternary chalcogeniden spinel family is well-known and has been extensively researched for decades. [17] They have face center cubic structure and is represented as AB 2 X 4 , where A and B are metal atoms that center the X (chalcogens) tetrahedrons and octahedrons, respectively. Almost all main group and transition metal elements may be synthesized in a stable spinel form, resulting in a diverse range of elemental compositions, electron configurations, and valence states.…”

Biphenylene monolayer as a two-dimensional nonbenzenoid carbon allotrope: A first-principles study

“…Carbon's ability to form in a variety of shapes through different dimensions has sparked interest in discovering additional allotropic forms made up of diverse networks of rings and polygons. To clarify, researchers have identified a wide range of carbon allotropes composed of sp 3 , sp 2 , and sp hybridized carbon atoms such as graphenylene, 1 graphdiyne, 2 graphyne, 3 cyclocarbons, 4 pentaheptite, 5 graphene, 6 phagraphene, 7 haeckelites, 8 pentahexoctite, 9 carbon nanotubes, 10 carbon nanocone, 11 and fullerene. 12 Owing to their electronic and mechanical properties, these materials have been widely advocated as a possible candidate for popularly used applications such as sensors, 13 energy storage, 14 nanoelectronic devices, 9 thermal rectifier, 15 etc.…”