发表机构
Ames National Laboratory; Department of Physics and Astronomy, Iowa State University; Department of Physics, The Pennsylvania State University（艾姆斯国家实验室; 爱荷华州立大学物理与天文系; 宾夕法尼亚州立大学物理系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过测量六个FeTe基异质结构的迈斯纳响应，发现界面约束超导电性呈强各向异性，可能具有线节点或深能隙极小值，并指出界面FeTe层为超导共同起源。
AI 中文摘要
界面约束超导电性源于电子态在化学性质不同的边界间的相互作用，为在磁性与拓扑共存区域工程化超导相提供了途径。然而，确定此类超导电性的内在本质颇具挑战性，因为超导层仅有几纳米厚，且被数层普通层掩埋。在此，我们利用频域隧道二极管谐振器，在均匀磁场中测量了六个FeTe基异质结构的全样品迈斯纳响应。在超薄极限下，所测磁化率的常规归一化χ(T→0)=-1会失效达数十个百分点。我们建立了适当的校准方法，并对χ(T)求逆以确定伦敦穿透深度λ(T)。由此得出两个关键结果。第一，χ(T)中观察到的宽转变自然源于极端几何形状和大λ值，无需化学或结构不均匀性；提取的λ(T)与电阻转变紧密吻合。第二，λ(T)及相应的超流密度与完全能隙的各向同性s波态不一致，反而表明存在强各向异性序参量，可能具有线节点或深能隙极小值。推断的λ(0)约为1微米，与二维相位刚度的独立分析一致。尽管三种覆盖层具有截然不同的化学、磁性和拓扑特性，但所有六个FeTe异质结构均表现出相似的低温幂律行为，且超导响应不系统依赖于覆盖层身份。这些结果表明界面FeTe层是超导电性的共同起源。
英文摘要
Interface-confined superconductivity emerges from the interaction of electronic states across chemically distinct boundaries, providing a route to engineer superconducting phases where magnetism and topology coexist. Determining the intrinsic nature of such superconductivity, however, is challenging because the superconducting layer is only a few nanometers thick and buried beneath several normal layers. Here, we measure the whole-sample Meissner response of six $\mathrm{FeTe}$-based heterostructures in a uniform magnetic field using a frequency-domain tunnel-diode resonator. In the ultrathin limit, the conventional normalization of the measured susceptibility, $χ(T\to0)=-1$, fails by tens of percent. We establish the appropriate calibration and invert $χ(T)$ to determine the London penetration depth $λ(T)$. Two key results emerge. First, the broad transitions observed in $χ(T)$ arise naturally from the extreme geometry and large $λ$, without requiring chemical or structural inhomogeneity; the extracted $λ(T)$ closely tracks the resistive transition. Second, $λ(T)$ and the corresponding superfluid density are inconsistent with a fully gapped isotropic $s$-wave state and instead indicate a strongly anisotropic order parameter possibly with line nodes or deep gap minima. The inferred $λ(0)$ is of order $1\,μ$m, consistent with an independent analysis of the 2D phase stiffness. Despite the distinct chemical, magnetic, and topological character of the three overlayers, all six FeTe heterostructures exhibit similar low-temperature power-law behavior, with no systematic dependence of the superconducting response on overlayer identity. These results point to the interfacial $\mathrm{FeTe}$ layer as the common origin of superconductivity.
