高度无序超导体绝缘相中“赝能隙”的本质
The nature of the "pseudogap" in the insulating phase of highly disordered superconductors
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中文总结 AI 辅助
结合超高阻平面隧穿谱测量与量子蒙特卡罗模拟，证实高度无序超导体绝缘相中的单粒子能隙随无序度增大，为库珀对绝缘态提供了直接实验确认，建立了两类赝能隙的统一关联。
中文摘要 AI 辅助
经历超导体-绝缘体转变的无序薄膜为研究无竞争电子序情况下的赝能隙物理提供了可控环境。尽管理论预测局域库珀对可在绝缘相深处存续，但直接的谱学确认仍无法通过实验实现，因为在高绝缘性薄膜中进行隧穿测量需要超高阻结和皮安级电流灵敏度。本研究结合对非晶氧化铟薄膜的超高阻平面隧穿谱测量与吸引哈伯德模型的量子蒙特卡罗模拟，探究绝缘态深处的单粒子激发谱。我们发现实验与理论存在显著一致性：单粒子能隙不仅在超导体-绝缘体转变过程中存续，还随无序度大幅增大，达到超导侧观测值的两倍以上；随温度升高，能隙逐渐填充而非关闭，同时相干峰被抑制，谱权重重新分布至远高于能隙尺度的能量区域。我们的结果为理论预测的、具有局域库珀对的库珀对绝缘态提供了直接定量实验确认，并确立了Tc以上的赝能隙与绝缘能隙之间的统一关联，二者均为无整体相位相干的配对行为的体现。
英文摘要
Disordered thin films undergoing a superconductor-insulator transition provide a controlled setting for studying pseudogap physics in the absence of competing electronic orders. Although theory predicts that local Cooper pairing can survive deep into the insulating phase, direct spectroscopic confirmation has remained experimentally inaccessible because tunneling measurements in highly insulating films require ultra-high-resistance junctions and picoampere current sensitivity. Here we combine ultra-high-resistance planar tunneling spectroscopy on amorphous indium oxide films with quantum Monte Carlo simulations of the attractive Hubbard model to probe the single-particle excitation spectrum deep in the insulating regime. We find striking agreement between experiment and theory: the single-particle gap not only survives across the superconductor-insulator transition, but increases substantially with disorder, reaching values more than twice those observed on the superconducting side. With increasing temperature, the gap fills rather than closes, while coherence peaks are suppressed and spectral weight redistributes to energies far exceeding the gap scale. Our results provide direct quantitative experimental confirmation of the theoretically predicted Cooper-pair insulating state with localized Cooper pairs and establish a unified connection between the pseudogap above $T_c$ and the insulating gap as manifestations of pairing without global phase coherence.
