Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-dimensional topological nodal line semimetal in layered $X_2Y$ ($X$
  = Ca, Sr, and Ba; $Y$ = As, Sb, and Bi)   In topological semimetals the Dirac points can form zero-dimensional and
one-dimensional manifolds, as predicted for Dirac/Weyl semimetals and
topological nodal line semimetals, respectively. Here, based on
first-principles calculations, we predict a topological nodal line semimetal
phase in the two-dimensional compounds $X_2Y$ ($X$=Ca, Sr, and Ba; $Y$=As, Sb,
and Bi) in the absence of spin-orbit coupling (SOC) with a band inversion at
the M point. The mirror symmetry as well as the electrostatic interaction, that
can be engineered via strain, are responsible for the nontrivial phase. In
addition, we demonstrate that the exotic edge states can be also obtained
without and with SOC although a tiny gap appears at the nodal line for the bulk
states when SOC is included.

23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
19
The categories of this paper are: eess
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math