Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous superconducting state gap size versus Tc behavior in
  underdoped Bi_2Sr_2Ca_1-xDy_xCu_2O_8+d   We report angle-resolved photoemission spectroscopy measurements of the
excitation gap in underdoped superconducting thin films of
Bi_2Sr_2Ca_{1-x}Dy_xCu_2O_{8+d}. As Tc is reduced by a factor of 2 by
underdoping, the superconducting state gap \Delta does not fall proportionally,
but instead stays constant or increases slightly, in violation of the BCS
mean-field theory result. The different doping dependences of \Delta and kT_c
indicate that they represent different energy scales. The measurements also
show that \Delta is highly anisotropic and consistent with a d_{x^2-y^2} order
parameter, as in previous studies of samples with higher dopings. However, in
these underdoped samples, the anisotropic gap persists well above T_c. The
existence of a normal state gap is related to the failure of \Delta to scale
with T_c in theoretical models that predict pairing without phase coherence
above T_c.

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The categories of this paper are: hep-ph
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex