Weak-coupling Bardeen-Cooper-Schrieffer superconductivity in the electron-doped cuprate superconductors

Shan, Lei; Huang, Yaobo; Wang, Yonglei; Li, Shiliang; Zhao, Jun; Dai, Pengcheng; Zhang, Y. Z.; Ren, Cong; Wen, Hao

doi:10.1103/physrevb.77.014526

Cited by 32 publications

(21 citation statements)

References 35 publications

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“…From fitting the subgap-shape of tunneling conductance by using extended Blonder-Tinkham-Klapwijk theory [11], the symmetry of order parameter favors d-wave or NMD, that is superconductivity of PLCCO with nodal gap. These results are almost consistent with other group's results [9]. We conclude that the characteristic features (such as d-wave order parameter and no pseudogap above T c ) in electron-doped cuprates in the overdoped regime are fundamentally similar to those in hole-doped cuprates in the overdoped regime.…”

Section: Discussionsupporting

confidence: 93%

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Temperature dependence of tunneling conductance on an overdoped Pr0.82LaCe0.18CuO4 with Tc∼16K

Minematsu

Fujita

Yamada

et al. 2010

Physica C: Superconductivity and its Applications

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Section: Discussionsupporting

confidence: 93%

“…For example, in an electrondoped system concerning to the symmetry of order parameter, some experimental data are favor for s-wave [4,5], but the other support the nodal gap [6]. Moreover, a recent ARPES study [7] suggests that the symmetry of order parameter is nonmonotonic dwave (NMD) and this result was supported by other studies [8,9].…”

Section: Introductionmentioning

confidence: 86%

Temperature dependence of tunneling conductance on an overdoped Pr0.82LaCe0.18CuO4 with Tc∼16K

Minematsu

Fujita

Yamada

et al. 2010

Physica C: Superconductivity and its Applications

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“…Horizontal bars on the plotted data represent three times the standard deviations in fitting FSs to the tight-binding model. For comparison, the values of T c of PLCCO and Pr 1− x LaCe x CuO 4 single crystals annealed by the conventional method263145, and those of the protect-annealed PLCCO single crystals (T. Adachi et al ., unpublished.) are also plotted against the Ce concentration x .…”

Section: Figurementioning

confidence: 99%

Suppression of the antiferromagnetic pseudogap in the electron-doped high-temperature superconductor by protect annealing

et al. 2016

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In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity. In the electron-doped cuprates, on the other hand, superconductivity appears only in a narrow window of high-doped Ce concentration after reduction annealing, and strong antiferromagnetic correlation persists in the superconducting phase. Recently, Pr1.3−xLa0.7CexCuO4 (PLCCO) bulk single crystals annealed by a protect annealing method showed a high critical temperature of around 27 K for small Ce content down to 0.05. Here, by angle-resolved photoemission spectroscopy measurements of PLCCO crystals, we observed a sharp quasi-particle peak on the entire Fermi surface without signature of an antiferromagnetic pseudogap unlike all the previous work, indicating a dramatic reduction of antiferromagnetic correlation length and/or of magnetic moments. The superconducting state was found to extend over a wide electron concentration range. The present results fundamentally challenge the long-standing picture on the electronic structure in the electron-doped regime.

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“…In each case, a parabolic fit ͑dashed lines͒ to high bias data, consistent with a voltage sweep at a temperature slightly above the T C of the crystal, was used to normalize the spectrum. 34 The normalized conductance spectra of the junctions at selected temperatures are shown in Figs. 2͑c͒ and 2͑d͒.…”

mentioning

confidence: 99%

“…The broadening term ␥ is typically less than 1 meV with a slight variation in the temperature range below T C . Although the reason for such a variation has not been unambiguously established, 34 the small lifetime broadening term does significantly increase the accuracy of the estimated gap size.…”

mentioning

confidence: 99%

Evidence of a universal and isotropic2Δ/kBTCratio in 122-type iron pnictide superconductors over a wide doping range

Zhang

Liu

et al. 2010

Phys. Rev. B

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We have systematically investigated the doping and the directional dependence of the gap structure in the 122-type iron pnictide superconductors by point contact Andreev reflection spectroscopy. The studies were performed on single crystals of Ba 1−x K x Fe 2 As 2 ͑x = 0.29, 0.49, and 0.77͒ and SrFe 1.74 Co 0.26 As 2 with a sharp tip of Pb or Au pressed along the c-axis or the ab-plane direction. The conductance spectra obtained on highly transparent contacts clearly show evidence of a robust superconducting gap. The normalized curves can be well described by the Blonder-Tinkham-Klapwijk model with a lifetime broadening. The determined gap value scales very well with the transition temperature, giving the 2⌬ / k B T C value of ϳ3.1. The results suggest the presence of a universal coupling behavior in this class of iron pnictides over a broad doping range and independent of the sign of the doping. Moreover, conductance spectra obtained on c-axis junctions and ab-plane junctions indicate that the observed gap is isotropic in these superconductors. The discovery of superconductivity in different classes of iron pnictides 1 has attracted great interest. To date, a widely discussed pairing theory for the superconductivity is the sϮ-wave symmetry 2 with nodeless gaps for both electron pockets and hole pockets and a sign reversal between them. Experimentally, a number of observations [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] have been suggested to be consistent with the sϮ-wave picture; however, there remain significant discrepancies in the reported results. First of all, at present there is no consensus on the value of the 2⌬ / k B T C ratio, 3-21 which represents the fundamental coupling strength of superconductivity. Moreover, it has been suggested that many experimental data can be explained with either the sϮ wave or a single gap picture, [10][11][12]14,[17][18][19][20][21] implying a lack of conclusive evidence for the multigap prediction of the sϮ wave in these measurements. Perhaps, the most intriguing observation comes from recent thermal transport measurements, in which a substantial residual 0 / T term at zero field was found in BaFe 2 As 2−x P x ͑Ref. 22͒ and KFe 2 As 2 ͑Ref. 23͒ single crystals, indicating the existence of line nodes in the energy gap of these superconductors. This particular result has lead to the speculation that perhaps the structure of the order parameter changes upon doping from nodeless to nodal. Clearly, a systematic doping dependent study of the order parameter is required to understand the pairing nature in the 122 type superconductors.As direct probes of the density of states, tunneling spectroscopy and point contact Andreev reflection ͑PCAR͒ spectroscopy have historically played central roles in investigating the superconducting gap. In addition to providing the measurement of the 2⌬ / k B T C ratio, the ability of these techniques to study the anisotropy and the temperature dependence of the gaps makes them a key tool in providing direct evidence for various mechani...

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Weak-coupling Bardeen-Cooper-Schrieffer superconductivity in the electron-doped cuprate superconductors

Cited by 32 publications

References 35 publications

Temperature dependence of tunneling conductance on an overdoped Pr0.82LaCe0.18CuO4 with Tc∼16K

Temperature dependence of tunneling conductance on an overdoped Pr0.82LaCe0.18CuO4 with Tc∼16K

Suppression of the antiferromagnetic pseudogap in the electron-doped high-temperature superconductor by protect annealing

Evidence of a universal and isotropic2Δ/kBTCratio in 122-type iron pnictide superconductors over a wide doping range

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