Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Josephson effect and Andreev reflection in Ba(1-x)NaxFe2As2 (x=0.25 and
  0.35) point contacts   I(V) characteristics and their first derivatives of ScS and ScN-type
(S-superconductor, c-constriction, N-normal metal) point-contacts (PCs) based
on Ba{1-x}NaxFe2As2 ($x$=0.25 and 0.35) were studied. ScS-type PCs with S=Nb,Ta
and Pb show Josephson-like resistively shunted I(V) curves with microwave
induced Shapiro steps which satisfy relation 2eV=hw. The I_cR_N product
(I_c-critical current, R_N-- normal state PC resistance) in these PCs is found
to be up to 1.2mV. All this data with the observed dependence of the I_c on the
microwave power of ScS PCs with Pb counterelectrode indicates the presence of
the singlet s-wave type pairing in Ba(1-x)NaxFe2As2. From the dV/dI(V) curves
of ScN-type PCs demonstrating Andreev-reflection like features, the
superconducting gap ratio 2\Delta/k_BT_c = 3.6 \pm 1 for the compound with
x=0.35 was evaluated. Analysis of these dV/dI(V) at high biases V, that is well
above \Delta, testifies transition to the thermal regime in PCs with a voltage
increase.

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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: math
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: gr-qc