Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nodeless vs nodal order parameters in LiFeAs and LiFeP superconductors   High-precision measurements of magnetic penetration depth $\lambda$ in clean
single crystals of LiFeAs and LiFeP superconductors reveal contrasting
low-energy quasiparticle excitations. In LiFeAs the low-temperature
$\lambda(T)$ shows a flat dependence indicative of a fully gapped state, which
is consistent with previous studies. In contrast, LiFeP exhibits a $T$-linear
dependence of superfluid density $\propto \lambda^{-2}$, indicating a nodal
superconducting order parameter. A systematic comparison of quasiparticle
excitations in the 1111, 122, and 111 families of iron-pnictide superconductors
implies that the nodal state is induced when the pnictogen height from the iron
plane decreases below a threshold value of $\sim 1.33$\,\AA.

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The categories of this paper are: q-alg
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The categories of this paper are: physics
2
The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: astro-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org