Superconductor/semiconductor-nanowire hybrid structures can serve as versatile building blocks to realize Majorana circuits or superconducting qubits based on quantized levels such as Andreev qubits. For all these applications it is essential that the superconductor-semiconductor interface is as clean as possible. Furthermore, the shape and dimensions of the superconducting electrodes needs to be precisely controlled. We fabricated self-defined InAs/Al core/shell nanowire junctions by a fully in-situ approach, which meet all these criteria. Transmission electron microscopy measurements confirm the sharp and clean interface between the nanowire and the in-situ deposited Al electrodes which were formed by means of shadow evaporation. Furthermore, we report on tunnel spectroscopy, gate and magnetic field-dependent transport measurements. The achievable short junction lengths,the observed hard-gap and the magnetic field robustness make this new hybrid structure very attractive for applications which rely on a precise control of the number of sub-gap states, like Andreev qubits or topological systems.

中文翻译：

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自定义介观InAs / Al纳米线约瑟夫森结中的硬隙光谱

超导体/半导体-纳米线混合结构可以用作通用的构建块，以基于诸​​如安德列夫量子位的量化水平实现马里亚纳电路或超导量子位。对于所有这些应用，超导体-半导体接口必须尽可能干净。此外，需要精确控制超导电极的形状和尺寸。我们通过完全原位方法制造了满足所有这些条件的自定义InAs / Al核/壳纳米线结。透射电子显微镜测量证实了纳米线和通过阴影蒸发形成的原位沉积的Al电极之间的清晰和干净的界面。此外，我们报告了隧道光谱，与门和磁场有关的传输测量。