High-Throughput Screening for Ideal 3D Carbon Topological Semimetals via Bottom-up Approach

Topological semimetals have attracted widespread attention due to their unique low-energy excitations. In the past few years, thousands of topological semimetals have been identified. However, few of them have desirable features for future practical applications and physical research, including a small attribution range of energy of the Dirac/Weyl nodes near the Fermi level, a large clean energy window around nodes, high Fermi velocities, and superb energy stability. Moreover, there is no highly effective method for the quantitative screening of the ideal topological semimetal materials. Herein, taking 3D carbon allotropes as an example, we first propose an "ideal index" for the high-throughput screening of ideal topological semimetals. Specifically, we first construct hundreds of new reasonable carbon allotropes with both sp2 and sp3 hybridization, via a bottom-up strategy. Then, the potential topological materials are screened using symmetry-based topological index theory. Subsequently, on the basis of the proposed "ideal index", 11 relatively ideal topological semimetals have been identified. Particularly, the best system, i.e., CNN-4(2,4), harbors a large clean window of 0.61 eV, a high Fermi velocity of 1.1 × 106 m/s (even larger than that of graphene), and a low cohesive energy, and the nodes are very close to the Fermi level. These results not only enrich the family of superb 3D carbon allotropes for the developing carbon-based electronics but also establish a quantitative scheme for the high-throughput searching for the needed topological semimetals.