发表机构
Institute of Industrial Science, The University of Tokyo; Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science（东京大学工业科学研究所; 物质材料研究机构纳米结构材料研究中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究了范德华超导准晶 (Ta$_{0.7}$Nb$_{0.3}$)$_{1.6}$Te 的上临界场，发现其具有各向异性、表面超导及低温下偏离传统理论的异常行为，并归因于电子扩散率的空间分布。
AI 中文摘要
我们研究了 Nb 取代的范德华层状准晶 (Ta$_{0.7}$Nb$_{0.3}$)$_{1.6}$Te 大单晶的上临界场。该样品在 $T_{\mathrm{c}}$ = 1.35 K 处表现出尖锐的超导转变，这是迄今报道的准晶超导体中的最高值。临界场的角度依赖性表现出显著的判据依赖性：使用 10% $R_{\mathrm{N}}$（$R_{\mathrm{N}}$：正常态电阻）判据确定的场可由各向异性 Ginzburg-Landau 模型很好地描述，而使用 65% 和 90% $R_{\mathrm{N}}$ 判据确定的场则表现出二维超导特有的 Tinkham 型角度依赖性。电阻转变的高场部分可由表面超导模型很好地描述，并且在接近 $ab$ 平面的磁场下表现出显著的激发电流依赖性，支持准周期 $ab$ 平面表面上存在表面超导。体态 $H_{\mathrm{c2}}$ 具有强各向异性，面内 $H_{\mathrm{c2}}$ 超过弱耦合 Pauli 极限约 2.5 倍。对于两种磁场取向，$H_{\mathrm{c2}}(T)$ 在低温下均偏离传统的脏极限 Werthamer-Helfand-Hohenberg 预测。包含电子扩散率空间分布的唯象修正 Ginzburg-Landau-Abrikosov-Gorkov 模型显著改善了对 $H_{\mathrm{c2}}(T)$ 的描述，表明电子输运性质的空间变化可能有助于其异常的温度依赖性。
英文摘要
We investigated the upper critical field of a large single grain of the Nb-substituted van der Waals layered quasicrystal (Ta$_{0.7}$Nb$_{0.3}$)$_{1.6}$Te. The sample exhibits a sharp superconducting transition at $T_{\mathrm{c}}$ = 1.35 K, the highest value reported to date among quasicrystal superconductors. The angular dependence of the critical field exhibits a pronounced criterion dependence: the field determined using the 10% $R_{\mathrm{N}}$ ($R_{\mathrm{N}}$: normal-state resistance) criterion is well described by the anisotropic Ginzburg-Landau model, whereas those determined using the 65% and 90% $R_{\mathrm{N}}$ criteria exhibit Tinkham-like angular dependence characteristic of two-dimensional superconductivity. The high-field part of the resistive transition is well described by a surface-superconductivity model and exhibits a pronounced excitation-current dependence for magnetic fields close to the $ab$ plane, supporting the presence of surface superconductivity on the quasiperiodic $ab$-plane surfaces. The bulk $H_{\mathrm{c2}}$ is strongly anisotropic, with the in-plane $H_{\mathrm{c2}}$ exceeding the weak-coupling Pauli limit by a factor of approximately 2.5. For both field orientations, $H_{\mathrm{c2}}(T)$ deviates upward from the conventional dirty-limit Werthamer-Helfand-Hohenberg prediction at low temperatures. A phenomenologically modified Ginzburg-Landau-Abrikosov-Gorkov model incorporating a spatial distribution of the electronic diffusivity substantially improves the description of $H_{\mathrm{c2}}(T)$, suggesting that spatial variations in electronic transport properties may contribute to its anomalous temperature dependence.
