Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chiral phonons in binary compounds $A$Bi ($A$ = K, Rb, Cs) with P2$_1$/c
  structure   Binary compounds $A$Bi ($A$ = K, Rb, Cs) crystallize in P2$_1$/c structure
containing both clockwise and anticlockwise chiral chains of Bi atoms.
Electronic band structure exhibits the insulating nature of these systems, with
the band gap about 0.25 eV. The presented study of dynamical properties confirm
a stability of the system with P2$_1$/c symmetry. Independently of the absence
of the three-fold (or higher) rotational symmetry axes, the chiral modes
propagate along the Bi atom chains in these systems. We discuss basic
properties of these modes in monoatomic chiral chains.

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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph