Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Local density of states and superconducting gap in the iron chalcogenide
  superconductor Fe$_{1+\delta}$Se$_{1-x}$Te$_{x}$ observed by scanning
  tunneling spectroscopy   We report on the first investigation of the quasiparticle local density of
states and superconducting gap in the iron chalcogenide superconductor
Fe$_{1+\delta}$Se$_{1-x}$Te$_{x}$ ($T_{\mathrm{c}} \sim 14$ K). The surface of
a cleaved crystal revealed an atomic square lattice, superimposed on the
inhomogeneous background, with a lattice constant of $\sim 3.8$ \AA without any
reconstruction. Tunneling spectra measured at 4.2 K exhibit the superconducting
gap, which completely disappears at 18 K, with a magnitude of $\sim 2.3$ meV,
corresponding to $2\Delta / k_{\mathrm{B}}T_{\mathrm{c}}=3.8$.In stark contrast
to the cuprate superconductors, the value of the observed superconducting gap
is relatively homogeneous, following a sharp distribution with a small standard
deviation of 0.23 meV. Conversely, the normal-state local density of states
observed above $T_{\mathrm{c}}$ shows spatial variation over a wide energy
range of more than 1 eV, probably due to the excess iron present in the
crystal.

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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: nlin
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph
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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph