Presentation Information
[ED3-03]Reveal inhomogeneities in a superconducting nanowire by probing and mapping self-heating hotspots
*Qingyuan Zhao1 (1. Nanjing University (China))
Keywords:
Superconducting nanowire,Inhomogeneities,Hotspot
The pursuit of uniform superconducting nanowires is paramount for advancing superconducting devices, particularly in single-photon detection, digital circuits and quantum computing. Although advanced nanofabrication techniques are applied, inhomogeneities, which are on orders of the coherent length in several nanometers, exist universally and affect the macroscopic superconducting phenomena in a long range. Consequently, the lack of the locations, numbers and their dependence on device performance prevents from clarifying superconducting switching mechanisms and optimizing performance further. In this talk, a hotspot scanning microscope (HSM) for locating and identifying inhomogeneities in situ and with nanoscale resolution will be introduced. This method leveraged the multi-photon detection mechanism and self-heating equilibrium in a superconducting nanowire to generate and manipulate a hotspot. The current-voltage (IV) relationship reflected the initialization and growth of the hotspot, from which the geometric variation can be reconstructed. In a 12 μm long nanowire, 50 different types of IV curves were found, revealing the large amount of inhomogeneities. When the hotspot shrunk to a minimum size (~100 nm) at a location considered as a local constriction, 23 constrictions were identified 23 local constrictions were identified, with their positions marked at a spatial resolution of ~100 nm. The resulting constriction map facilitated the localization of dark count sources with enhanced spatial resolution and allowed for the separation of their contributions to the total counts. This work demonstrates the ubiquitous presence of inhomogeneities and clarifies their influence on device performance, providing a foundation for future optimization and engineering efforts.