Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Emergence of Topological insulator and Nodal line semi-metal states in
  XX'Bi (X=Na, K, Rb, Cs; X'=Ca, Sr)   In this letter, we predict the emergence of non-trivial band topology in the
family of XX'Bi compounds having $P\overline{6}2m$ (\# 189) space group. Using
first principles calculations within hybrid functional framework, we
demonstrate that NaSrBi and NaCaBi are strong topological insulator under
controlled band engineering. Here, we propose three different ways to engineer
the band topology to get a non-trivial order: (i) hydrostatic pressure, (ii)
biaxial strain (due to epitaxial mismatch), and (iii) doping. Non-triviality is
confirmed by investigating bulk band inversion, topological Z$_2$ invariant,
surface dispersion and spin texture. Interestingly, some of these compounds
also show a three dimensional topological nodal line semi-metal (NLS) state in
the absence of spin orbit coupling (SOC). In these NLS phases, the closed loop
of band degeneracy in the Brillouin zone lie close to the Fermi level.
Moreover, a drumhead like flat surface state is observed on projecting the bulk
state on the [001] surface. The inclusion of SOC opens up a small band gap
making them behave like a topological insulator.

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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc