Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for Two-Band Superconductivity from Break Junction Tunneling on
  MgB2   Superconductor-insulator-superconductor tunnel junctions have been fabricated
on MgB2 that display Josephson and quasiparticle currents. These junctions
exhibit a gap magnitude, Delta~2.5 meV, that is considerably smaller than the
BCS value, but which clearly and reproducibly closes near the bulk Tc. In
conjunction with fits of the conductance spectra, these results are interpreted
as direct evidence of two-band superconductivity.

25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
19
The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: stat
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
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The categories of this paper are: alg-geom