Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quasiparticle density of states in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$
  single crystals probed using tunneling spectroscopy at ultra-low temperatures
  in high magnetic fields   Break-junction tunneling spectroscopy at temperatures 30-50 mK in high
magnetic field is used to directly probe the quasiparticle density of states
within the energy gap in a single crystal Bi2212 high-$T_c$ superconductor. The
measured tunneling conductances $dI/dV(V)$ in the subgap region have a zero
flat region with no evidence for a linear increase of the density of states
with voltage. A number of tunnel break-junctions exhibited $dI/dV(V)$ curves
with a second energy gap structure at the average magnitude 2$\Delta
_{p-p}/e=13$ mV. Our data cannot be explained by either a pure $s$ pairing or a
pure $d_{x^2-y^2}$ pairing.

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The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th