Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Andreev reflections and tunneling spectroscopy on underdoped NCCO (x =
  0.15)   Andreev-reflection and tunneling studies have been carried out on a single
crystal of underdoped Nd1.85Ce0.15CuO4-d (NCCO) by using Ag, Pt-Ir and Nb tips
to clarify the symmetry of its order parameter. Surprisingly, we observed in
the NCCO, on the one hand, the Josephson current (with Nb tip) which indicates
the presence of s-wave order parameter, on the other hand, a zero-bias
conductance peak (with Ag tip) which is a manifestation of d-wave order
parameter. In addition, we find the presence of two distinct energy scales in
the underdoped NCCO: the smallest energy scale is associated with the Andreev
gap and c-axis tunneling gap, and the second scale corresponds to the maximum
in-plane tunneling gap. It seems that the phenomenon of superconductivity in
electron- and hole-doped cuprates can be understood within a common scheme.

12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat