Energy gap evolution across the superconductivity dome in single crystals of (Ba(1-x) K (x) )Fe(2)As(2).
Energy gap evolution across the superconductivity dome in single crystals of (Ba(1-x) K (x) )Fe(2)As(2).
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DOI：
10.1126/sciadv.1600807
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发表时间：
2016-09
期刊：
影响因子：
13.6
通讯作者：
Prozorov R
中科院分区：
文献类型：
--
作者：
Cho K;Kończykowski M;Teknowijoyo S;Tanatar MA;Liu Y;Lograsso TA;Straszheim WE;Mishra V;Maiti S;Hirschfeld PJ;Prozorov R
采用控制无序法研究了（Ba1−xKx）Fe2As2的超导能隙。铁基超导体的非常规超导机制是当前材料研究中最令人感兴趣的问题之一。在非氧化物ibs中，（Ba1−xKx）Fe2As2由于其高超导转变温度和从最佳掺杂（x≈0.4）时完全各向同性到x > 0.8时变为节点的超导间隙结构的迷人演变而得到了广泛的研究。虽然在几个独立的实验中发现了这种显著的演变，但由于缺乏覆盖整个超导圆顶k掺杂范围的高质量单晶，迄今为止还没有关于间隙演变的细节。我们系统地研究了2.5 mev电子辐照引起的不同浓度点状缺陷在全相图上的伦敦穿透深度λ(T)。利用幂律Δλ ~ Tn拟合低温变化，发现在最优掺杂时n指数最高，Tc抑制率最小，并且随着掺杂离最优掺杂的距离而变化，这与间隙各向异性的增加相一致，其中在x≈0.8处发生突变，表明节点行为开始。我们使用自洽t矩阵方法的分析表明，在ibs中s±配对的普遍和鲁棒性，并反对先前提出的在该系统中x = 1附近向d波状态的过渡。
Controlled disorder was used to study the superconducting energy gap in (Ba1−xKx)Fe2As2. The mechanism of unconventional superconductivity in iron-based superconductors (IBSs) is one of the most intriguing questions in current materials research. Among non-oxide IBSs, (Ba1−xKx)Fe2As2 has been intensively studied because of its high superconducting transition temperature and fascinating evolution of the superconducting gap structure from being fully isotropic at optimal doping (x ≈ 0.4) to becoming nodal at x > 0.8. Although this marked evolution was identified in several independent experiments, there are no details of the gap evolution to date because of the lack of high-quality single crystals covering the entire K-doping range of the superconducting dome. We conducted a systematic study of the London penetration depth, λ(T), across the full phase diagram for different concentrations of point-like defects introduced by 2.5-MeV electron irradiation. Fitting the low-temperature variation with the power law, Δλ ~ Tn, we find that the exponent n is the highest and the Tc suppression rate with disorder is the smallest at optimal doping, and they evolve with doping being away from optimal, which is consistent with increasing gap anisotropy, including an abrupt change around x ≃ 0.8, indicating the onset of nodal behavior. Our analysis using a self-consistent t-matrix approach suggests the ubiquitous and robust nature of s± pairing in IBSs and argues against a previously suggested transition to a d-wave state near x = 1 in this system.