Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vortex Lattice Melting and Hc2 in underdoped YBa2Cu3Oy   Vortices in a type-II superconductor form a lattice structure that melts when
the thermal displacement of the vortices is an appreciable fraction of the
distance between vortices. In an anisotropic high-Tc superconductor, such as
YBa2Cu3Oy, the magnetic field value where this melting occurs can be much lower
than the mean-field critical field Hc2. We examine this melting transition in
YBa2Cu3Oy with oxygen content y from 6.45 to 6.92, and fit the data to a theory
of vortex-lattice melting. The quality of the fits indicates that the
transition to a resistive state is indeed the vortex lattice melting
transition, with the shape of the melting curves being consistent with the
known change in penetration depth anisotropy from underdoped to optimally doped
YBa2Cu3Oy. From the fits we extract Hc2(T = 0) as a function of hole doping.
The unusual doping dependence of Hc2(T =0) points to some form of electronic
order competing with superconductivity around 0.12 hole doping.

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The categories of this paper are: comp-gas
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: q-bio
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The categories of this paper are: chem-ph