Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phonon-drag induced suppression of the Andreev hole current in
  superconducting niobium contacts   We have investigated how the Andreev-reflection hole current at ballistic
point contacts responds to a large bias voltage. Its strong suppression could
be explained by the drag excerted by the non-equilibrium phonon wind generated
by high-energy electrons flowing through the contact. The hole - phonon
interaction leads to scattering lengths of the low-energetic holes down to
100\,nm, thereby destroying the coherent retracing of the electron path by the
Andreev-reflected holes.

31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math