AI 中文总结
该研究以拓扑绝缘体纳米SQUID为对象，观测到通量驱动的全局超导相变及局域电导频谱跳变，但局域零偏峰与全局特征无关联，提出需结合全局拓扑性质与多类探针明确识别马约拉纳束缚态。
AI 中文摘要
拓扑系统由全局性质定义，这些性质强制局域边界模式的存在。三维拓扑绝缘体（TIs）是最早被提出承载拓扑超导性的体系之一，但后续实验焦点转移到了其他平台。本研究利用柱状纳米超导量子干涉器件（nano-SQUID）结构重新研究体绝缘TIs，该几何结构优化了TI表面的邻近效应，可通过nano-SQUID的临界电流探测全局超导性质，同时通过隧道结探测nano-SQUID两端的局域态。我们观测到多个全局超导特征，包括周期性临界电流振荡、超导二极管效应的符号反转，这些特征似乎表明存在通量驱动的全局相变，符合进入拓扑区域的预期。同时，隧穿谱揭示了局域和非局域电导中的频谱跳变，与这些全局特征一致。然而，局域电导中的零偏峰（ZBPs）既出现在预测的磁场拓扑范围内，也出现在理论上的平凡区域（包括零磁场下）。最终，局域ZBP信号与全局信号缺乏相关性，这强调了要明确识别马约拉纳束缚态，必须采用综合方法，将全局拓扑性质的确定与局域及其他更先进探针的使用相结合。
英文摘要
Topological systems are defined by global properties that enforce the existence of local boundary modes. Three-dimensional topological insulators (TIs) were among the earliest proposed systems for hosting topological superconductivity, but experimental focus subsequently shifted to other platforms. Here, we revisit bulk-insulating TIs using a columnar nano-superconducting quantum interference device (nano-SQUID) architecture. This geometry optimises the proximity effect on the TI surface and enables simultaneous probing of global superconducting properties - via the critical current through the nano-SQUID - alongside the local states at the ends of the nano-SQUID via tunnel junctions. We observe several global superconducting features that appear to show a flux-driven global phase transition consistent with entering the topological regime, including periodic critical current oscillations and a sign reversal in the superconducting diode effect. Simultaneously, tunnelling spectroscopy reveals spectral jumps in local and nonlocal conductance that align with these global features. However, zero-bias peaks (ZBPs) in local conductance are present both within the predicted topological range of magnetic fields and in theoretically trivial regimes, including at zero magnetic field. Ultimately, the lack of correlation between local ZBP signatures and global signatures emphasises that conclusively identifying Majorana bound states will necessitate a combined approach, integrating the establishment of global topological properties with the use of local and other, more advanced, probes.
CommentsMain text: 8 pages, 4 figures. SM: 7 pages, 5 figures
