Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Steps in the Negative-Differential-Conductivity Regime of a
  Superconductor   Current-voltage characteristics were measured in the mixed state of
Y1Ba2Cu3O(7-delta) superconducting films in the regime where flux flow becomes
unstable and the differential conductivity dj/dE becomes negative. Under
conditions where its negative slope is steep, the j(E) curve develops a
pronounced staircase like pattern. We attribute the steps in j(E) to the
formation of a dynamical phase consisting of the succesive nucleation of
quantized distortions in the local vortex velocity and flux distribution within
the moving flux matter.

16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th