Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structural distortion behind the nematic superconductivity in
  Sr$_x$Bi$_2$Se$_3$   An archetypical layered topological insulator Bi$_2$Se$_3$ becomes
superconductive upon doping with Sr, Nb or Cu. Superconducting properties of
these materials in the presence of in-plane magnetic field demonstrate
spontaneous symmetry breaking: 180$^\circ$-rotation symmetry of
superconductivity versus 120$^\circ$-rotation symmetry of the crystal. Such
behavior brilliantly confirms nematic topological superconductivity. To what
extent this nematicity is due to superconducting pairing in these materials,
rather than due to crystal structure distortions? This question remained
unanswered, because so far no visible deviations from the 3-fold crystal
symmetry were resolved in these materials. To address this question we grow
high quality single crystals of Sr$_x$Bi$_2$Se$_3$, perform detailed X-ray
diffraction and magnetotransport studies and reveal that the observed
superconducting nematicity direction correlates with the direction of small
structural distortions in these samples( $\sim 0.02$\% elongation in one
crystallographic direction). Additional anisotropy comes from orientation of
the crystallite axes. 2-fold symmetry of magnetoresistance observed in the most
uniform crystals well above critical temperature demonstrates that these
structural distortions are nevertheless strong enough. Our data in combination
with strong sample-to-sample variation of the superconductive anisotropy
parameter are indicative for significance of the structural factor in the
apparent nematic superconductivity in Sr$_x$Bi$_2$Se$_3$.

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The categories of this paper are: mtrl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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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: atom-ph
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The categories of this paper are: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
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The categories of this paper are: eess