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首页> 外文期刊>Physical review >Doping and critical-temperature dependence of the energy gaps in Ba(Fe_(1-x)Co_x)_2As_2 thin films
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Doping and critical-temperature dependence of the energy gaps in Ba(Fe_(1-x)Co_x)_2As_2 thin films

机译：Ba（Fe_（1-x）Co_x）_2As_2薄膜中能隙的掺杂和临界温度依赖性

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摘要

The dependence of the superconducting gaps in epitaxial Ba(Fe_(1-x)Co_x)_2As_2 thin films on the nominal doping x (0.04 is contained in x is contained in 0.15) was studied by means of point-contact Andreev-reflection spectroscopy. The normalized conductance curves were well fitted by using the two-dimensional Blonder-Tinkham-Klapwijk model with two nodeless, isotropic gaps-although the possible presence of gap anisotropies cannot be completely excluded. The amplitudes of the two gaps Δ_S and Δ_L show similar monotonic trends as a function of the local critical temperature T_C~A (measured in the same point contacts) from 25 K down to 8 K. The dependence of the gaps on x is well correlated to the trend of the critical temperature, i.e., to the shape of the superconducting region in the phase diagram. When analyzed within a simple three-band Eliashberg model, this trend turns out to be compatible with a mechanism of superconducting coupling mediated by spin fluctuations, whose characteristic energy scales with Tc according to the empirical law Ω_0 = 4.65k_BT_C, and with a total electron-boson coupling strength λ_(tot) = 2.22 for x is contained in 0.10 (i.e., up to optimal doping) that slightly decreases to λ_(tot) = 1.82 in the overdoped samples (x = 0.15).
机译：通过点接触安德列夫反射光谱法研究了外延Ba（Fe_（1-x）Co_x）_2As_2薄膜中超导间隙对标称掺杂量x（x中包含0.04，0.15中包含）的依赖性。使用二维Blonder-Tinkham-Klapwijk模型和两个无节点的各向同性间隙，可以很好地拟合归一化​​的电导曲线，尽管不能完全排除间隙各向异性的可能。两个间隙的幅度Δ_S和Δ_L表现出相似的单调趋势，这是局部临界温度T_C〜A（在同一点接触中测量）从25 K到8 K的函数。间隙对x的依赖性很好临界温度的趋势，即相图中超导区域的形状。当在简单的三频带Eliashberg模型中进行分析时，这种趋势证明与自旋涨落介导的超导耦合机制兼容，自旋涨落的特征能量根据经验定律与Tc成比例，根据经验定律Ω_0= 4.65k_BT_C，与总电子成比例-x的玻色子耦合强度λ_（tot）= 2.22包含在0.10（即，达到最佳掺杂）中，在过量掺杂的样品中（x = 0.15），其稍微降低到λ_（tot）= 1.82。

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  • 来源
    《Physical review》 |2013年第17期|174506.1-174506.9|共9页
  • 作者

    P. Pecchio; D. Daghero; G. A. Ummarino; R. S. Gonnelli; F. Kurth; B. Holzapfel; K. Iida;

  • 作者单位

    Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino, Italy;

    Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino, Italy;

    Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino, Italy;

    Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino, Italy;

    Leibniz-Institut fuer Festkoerper-und Werkstoffforschung (IFW) Dresden, P.O. Box 270116, 01171 Dresden, Germany;

    Leibniz-Institut fuer Festkoerper-und Werkstoffforschung (IFW) Dresden, P.O. Box 270116, 01171 Dresden, Germany;

    Leibniz-Institut fuer Festkoerper-und Werkstoffforschung (IFW) Dresden, P.O. Box 270116, 01171 Dresden, Germany;

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  • 关键词

    proximity effects; Andreev effect; SN and SNS junctions; superconducting films and low-dimensional structures;

    机译：邻近效应;安德列夫效应;SN和SNS交界处;超导膜和低维结构;

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