QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ, Delft, The Netherlands.
Department of Applied Physics, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands.
Nat Commun. 2023 Jun 7;14(1):3325. doi: 10.1038/s41467-023-39044-w.
The proximity effect in semiconductor-superconductor nanowires is expected to generate an induced gap in the semiconductor. The magnitude of this induced gap, together with the semiconductor properties like spin-orbit coupling and g-factor, depends on the coupling between the materials. It is predicted that this coupling can be adjusted through the use of electric fields. We study this phenomenon in InSb/Al/Pt hybrids using nonlocal spectroscopy. We show that these hybrids can be tuned such that the semiconductor and superconductor are strongly coupled. In this case, the induced gap is similar to the superconducting gap in the Al/Pt shell and closes only at high magnetic fields. In contrast, the coupling can be suppressed which leads to a strong reduction of the induced gap and critical magnetic field. At the crossover between the strong-coupling and weak-coupling regimes, we observe the closing and reopening of the induced gap in the bulk of a nanowire. Contrary to expectations, it is not accompanied by the formation of zero-bias peaks in the local conductance spectra. As a result, this cannot be attributed conclusively to the anticipated topological phase transition and we discuss possible alternative explanations.
半导体-超导体纳米线中的近邻效应预计会在半导体中产生一个诱导能隙。这个诱导能隙的大小，以及自旋轨道耦合和 g 因子等半导体性质，取决于材料之间的耦合。据预测，这种耦合可以通过电场来调节。我们使用非局域光谱学研究了 InSb/Al/Pt 杂化材料中的这种现象。我们表明，可以对这些杂化材料进行调谐，以使半导体和超导体能够强烈耦合。在这种情况下，诱导能隙类似于 Al/Pt 壳中的超导能隙，只有在高磁场下才会关闭。相比之下，如果抑制耦合，就会导致诱导能隙和临界磁场的强烈减小。在强耦合和弱耦合区域之间的交叉点处，我们观察到纳米线体中的诱导能隙的关闭和重新打开。与预期相反，这并没有伴随着局域电导谱中零偏压峰的形成。因此，这不能被明确归因于预期的拓扑相变，我们讨论了可能的替代解释。
