Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct observation of nanoscale interface phase in the superconducting
  chalcogenide K$_{x}$Fe$_{2-y}$Se$_2$ with intrinsic phase separation   We have used scanning micro x-ray diffraction to characterize different
phases in superconducting K$_{x}$Fe$_{2-y}$Se$_2$ as a function of temperature,
unveiling the thermal evolution across the superconducting transition
temperature (T$_c\sim$32 K), phase separation temperature (T$_{ps}\sim$520 K)
and iron-vacancy order temperature (T$_{vo}\sim$580 K). In addition to the
iron-vacancy ordered tetragonal magnetic phase and orthorhombic metallic
minority filamentary phase, we have found a clear evidence of the interface
phase with tetragonal symmetry. The metallic phase is surrounded by this
interface phase below $\sim$300 K, and is embedded in the insulating texture.
The spatial distribution of coexisting phases as a function of temperature
provides a clear evidence of the formation of protected metallic percolative
paths in the majority texture with large magnetic moment, required for the
electronic coherence for the superconductivity. Furthermore, a clear
reorganization of iron-vacancy order around the T$_{ps}$ and T$_c$ is found
with the interface phase being mostly associated with a different iron-vacancy
configuration, that may be important for protecting the percolative
superconductivity in K$_{x}$Fe$_{2-y}$Se$_2$.

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The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: astro-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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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: adap-org
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The categories of this paper are: q-alg
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The categories of this paper are: nlin