发表机构
Cornell University; The Pennsylvania State University; University of Florida（康奈尔大学; 宾夕法尼亚州立大学; 佛罗里达大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过多种实验与理论手段，证实化学计量比FeTe具有节点超导性，为铁硫族超导理论提供新基准。
AI 中文摘要
化学计量比FeTe中的超导性为研究Fe(Se,Te)相图的FeTe端点提供了途径，然而其超导配对态的本质仍未得到解决。在本工作中，我们结合扫描超导量子干涉仪（SQUID）显微镜、电输运、扫描隧道显微镜与谱学（STM/S）以及平均场计算，研究了具有可调化学计量比的FeTe薄膜的局域超流体响应和配对态。即使在化学计量比FeTe中，我们观察到超流体刚度与超导转变温度$T_c$在微米尺度上的空间变化，而伦敦穿透深度在低至0.02$T_c$的温度下仍不饱和，并遵循指数约为1-1.5的幂律温度依赖关系。结合V形低能态密度和双能隙建模，这些结果表明超导态具有能隙节点或深能隙极小值，与$d$波或节点$s$波超导态一致。我们的发现确立了化学计量比FeTe作为一个独特的超导区域，偏离了在中等Se/Te组分下向更各向同性能隙发展的趋势，为铁硫族化物超导的现代微观理论提供了新的基准。我们的工作还揭示了随着超流体刚度降低，$T_c$从弱抑制到快速抑制的交叉行为，将FeTe与非常规超导体中观察到的更广泛现象联系起来。
英文摘要
Superconductivity in stoichiometric FeTe opens access to the FeTe endpoint of the Fe(Se,Te) phase diagram, yet the nature of its superconducting pairing state remains unresolved. In this work, we combine scanning superconducting quantum interference device (SQUID) microscopy, electrical transport, scanning tunneling microscopy and spectroscopy (STM/S), and mean-field calculations to investigate the local superfluid response and pairing state of FeTe thin films with tunable stoichiometry. Even in stoichiometric FeTe, we observe micrometer-scale spatial variations in both superfluid stiffness and superconducting transition temperature $T_c$, while the London penetration depth remains non-saturating down to 0.02$T_c$ and follows a power-law temperature dependence with an exponent of approximately 1-1.5. Together with a V-shaped low-energy density of states and two-gap modeling, these results indicate a superconducting state with gap nodes or deep minima, consistent with either a $d$-wave or nodal $s$-wave superconducting state. Our findings establish stoichiometric FeTe as a distinct superconducting regime that departs from the trend toward more isotropic gaps at intermediate Se/Te compositions, providing a new benchmark for modern microscopic theories of iron-chalcogenide superconductivity. Our work also reveals a crossover from weak to rapid suppression of $T_c$ as superfluid stiffness decreases, connecting FeTe to the broader phenomenology observed in unconventional superconductors.
Comments14 pages, 5 figures, with Supplementary Information. Comments are welcome
