Levajac Vukan, Wang Ji-Yin, Sfiligoj Cristina, Lemang Mathilde, Wolff Jan Cornelis, Bordin Alberto, Badawy Ghada, Gazibegovic Sasa, Bakkers Erik P A M, Kouwenhoven Leo P
QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2628GA, Delft, The Netherlands.
Beijing Academy of Quantum Information Sciences, 100193, Beijing, China.
Nat Commun. 2023 Oct 20;14(1):6647. doi: 10.1038/s41467-023-42422-z.
Tunneling spectroscopy is widely used to examine the subgap spectra in semiconductor-superconductor nanostructures when searching for Majorana zero modes (MZMs). Typically, semiconductor sections controlled by local gates at the ends of hybrids serve as tunnel barriers. Besides detecting states only at the hybrid ends, such gate-defined tunnel probes can cause the formation of non-topological subgap states that mimic MZMs. Here, we develop an alternative type of tunnel probes to overcome these limitations. After the growth of an InSb-Al hybrid nanowire, a precisely controlled in-situ oxidation of the Al shell is performed to yield a nm-thick AlOx layer. In such thin isolating layer, tunnel probes can be arbitrarily defined at any position along the hybrid nanowire by shadow-wall angle-deposition of metallic leads. In this work, we make multiple tunnel probes along single nanowire hybrids and successfully identify Andreev bound states (ABSs) of various spatial extension residing along the hybrids.
在寻找马约拉纳零模（MZMs）时，隧穿光谱被广泛用于研究半导体 - 超导体纳米结构中的能隙以下光谱。通常，混合结构两端由局部栅极控制的半导体部分充当隧道势垒。除了仅在混合结构末端检测态之外，这种由栅极定义的隧道探针会导致形成模仿MZMs的非拓扑能隙以下态。在这里，我们开发了一种替代类型的隧道探针来克服这些限制。在生长InSb - Al混合纳米线之后，对Al壳层进行精确控制的原位氧化，以产生纳米厚的AlOx层。在这种薄隔离层中，可以通过金属引线的阴影壁角沉积在沿混合纳米线的任何位置任意定义隧道探针。在这项工作中，我们沿着单纳米线混合结构制作了多个隧道探针，并成功识别了沿混合结构存在的各种空间扩展的安德列夫束缚态（ABSs）。
