Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Polar State induced by Block-type Lattice Distortions in BaFe2Se3 with
  Quasi-One-Dimensional Ladder Structure   Temperature dependent crystal structures of the quasi-one-dimensional ladder
material BaFe2Se3 are examined. Combining the optical second harmonic
generation (SHG) experiments and neutron diffraction measurements, we elucidate
the crystal structure with Pmn2_1 space group in the low-temperature phase
below Ts2 = 400 K, further above Neel temperature. This low-temperature phase
loses the spatial inversion symmetry, where a resultant macroscopic
polarization emerges along the rung direction. The transition is characterized
by block-type lattice distortions with the magneto-striction mechanism. Change
in the electrical resistivity and the magnetic susceptibility across the
polar-nonpolar transition also suggests a modification of the electronic states
reflecting the structural instability. Consistency and discrepancy with the
existing theory are discussed.

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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga