Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Negative differential resistance in normal narrow bands -
  superconducting junctions with Andreev reflection   We have calculated current-voltage characteristic curves for
normal-superconducting junctions with Andreev reflections and different types
of electronic bands. We found that when the normal band is narrow, of the order
of the superconducting energy gap, a negative differential resistance appears
at a voltage of the order of the band width plus the gap value. In case two
bands contribute to the total current the conductance can be smaller than unity
at voltages above the gap value. Our simulations may provide an answer to
different experimental data of the literature that were not yet understood.

33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
16
The categories of this paper are: stat