Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Disappearance of Nodal Gap across the Insulator-Superconductor
  Transition in a Copper-Oxide Superconductor   The parent compound of the copper-oxide high temperature superconductors is a
Mott insulator. Superconductivity is realized by doping an appropriate amount
of charge carriers. How a Mott insulator transforms into a superconductor is
crucial in understanding the unusual physical properties of high temperature
superconductors and the superconductivity mechanism. Here we report high
resolution angle-resolved photoemission measurement on heavily underdoped
Bi2Sr2-xLaxCuO6+d system. The electronic structure of the lightly-doped samples
exhibit a number of characteristics: existence of an energy gap along the nodal
direction, d-wave-like anisotropic energy gap along the underlying Fermi
surface, and coexistence of a coherence peak and a broad hump in the
photoemission spectra. Our results reveal a clear insulator-superconductor
transition at a critical doping level of ~0.10 where the nodal energy gap
approaches zero, the three-dimensional antiferromagnetic order disappears, and
superconductivity starts to emerge. These observations clearly signal a close
connection between the nodal gap, antiferromagnetism and superconductivity.

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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph