Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Dirac-Weyl semimetal: Coexistence of Dirac and Weyl fermions in
  polar hexagonal $ABC$ crystals   We propose that the noncentrosymmetric LiGaGe-type hexagonal $ABC$ crystal
SrHgPb realizes a new type of topological semimetal that hosts both Dirac and
Weyl points in momentum space. The symmetry-protected Dirac points arise due to
a band inversion and are located on the sixfold rotation $z$-axis, whereas the
six pairs of Weyl points related by sixfold symmetry are located on the
perpendicular $k_z=0$ plane. By studying the electronic structure as a function
of the buckling of the HgPb layer, which is the origin of inversion symmetry
breaking, we establish that the coexistence of Dirac and Weyl fermions defines
a phase separating two topologically distinct Dirac semimetals. These two Dirac
semimetals are distinguished by the $\mathbb{Z}_2$ index of the $k_z=0$ plane
and the corresponding presence or absence of 2D Dirac fermions on side
surfaces. We formalize our first-principles calculations by deriving and
studying a low-energy model Hamiltonian describing the Dirac-Weyl semimetal
phase. We conclude by proposing several other materials in the
non-centrosymmetric $ABC $ material class, in particular SrHgSn and CaHgSn, as
candidates for realizing the Dirac-Weyl semimetal.

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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
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The categories of this paper are: econ
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
9
The categories of this paper are: nlin