Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin pseudo-gap and interplane coupling in Y_2Ba_4Cu_7O_{15}: a ^{63}Cu
  nuclear spin-spin relaxation study   We report measurements of the Gaussian contribution, T_{2G}, to the plane
^{63}Cu nuclear spin--spin relaxation time in the YBa_2Cu_3O_7 and YBa_2Cu_4O_8
blocks of normal and superconducting Y_2Ba_4Cu_7O_{15}. The data confirm our
previous results that adjacent CuO_2 planes have different doping levels and
that these planes are strongly coupled. -- The static spin susceptibility at
the anti-ferromagnetic wave vector exhibits a Curie--Weiss like temperature
dependence in the normal state. -- The Y_2Ba_4Cu_7O_{15} data are incompatible
with a phase diagram based on a single CuO_2 plane theory and suggest that the
appearance of a spin gap implies interplane coupling. Additional data for
YBa_2Cu_4O_8 and YBa_2Cu_3O_{6.982} are in accord with the single plane theory.
-- The temperature dependence of T_{2G,ind} below T_c excludes isotropic s-wave
superconductivity in all three compounds.

27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol