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.