Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Normal metal - insulator - superconductor interferometer   Hybrid normal metal - insulator - superconductor microstructures suitable for
studying an interference of electrons were fabricated. The structures consist
of a superconducting loop connected to a normal metal electrode through a
tunnel barrier . An optical interferometer with a beam splitter can be
considered as a classical analogue for this system. All measurements were
performed at temperatures well below 1 K. The interference can be observed as
periodic oscillations of the tunnel current (voltage) through the junction at
fixed bias voltage (current) as a function of a perpendicular magnetic field.
The magnitude of the oscillations depends on the bias point. It reaches a
maximum at energy $eV$ which is close to the superconducting gap and decreases
with an increase of temperature. Surprisingly, the period of the oscillations
in units of magnetic flux $\Delta \Phi$ is equal neither to $h/e$ nor to
$h/2e$, but significantly exceeds these values for larger loop circumferences.
The origin of the phenomena is not clear.

13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex