QuTech and Kavli Institute of NanoScience , Delft University of Technology , 2600 GA Delft , The Netherlands.
Department of Applied Physics , Eindhoven University of Technology , 5600 MB Eindhoven , The Netherlands.
Nano Lett. 2018 Oct 10;18(10):6121-6128. doi: 10.1021/acs.nanolett.8b01534. Epub 2018 Sep 18.
Semiconductor nanowires such as InAs and InSb are promising materials for studying Majorana zero modes and demonstrating non-Abelian particle exchange relevant for topological quantum computing. While evidence for Majorana bound states in nanowires has been shown, the majority of these experiments are marked by significant disorder. In particular, the interfacial inhomogeneity between the superconductor and nanowire is strongly believed to be the main culprit for disorder and the resulting "soft superconducting gap" ubiquitous in tunneling studies of hybrid semiconductor-superconductor systems. Additionally, a lack of ballistic transport in nanowire systems can create bound states that mimic Majorana signatures. We resolve these problems through the development of selective-area epitaxy of Al to InSb nanowires, a technique applicable to other nanowires and superconductors. Epitaxial InSb-Al devices generically possess a hard superconducting gap and demonstrate ballistic 1D superconductivity and near-perfect transmission of supercurrents in the single mode regime, requisites for engineering and controlling 1D topological superconductivity. Additionally, we demonstrate that epitaxial InSb-Al superconducting island devices, the building blocks for Majorana-based quantum computing applications, prepared using selective-area epitaxy can achieve micron-scale ballistic 1D transport. Our results pave the way for the development of networks of ballistic superconducting electronics for quantum device applications.
半导体纳米线，如 InAs 和 InSb，是研究马约拉纳零模和展示拓扑量子计算中相关非阿贝尔粒子交换的有前途的材料。虽然已经证明了纳米线中的马约拉纳束缚态的存在，但这些实验中的大多数都存在显著的无序性。特别是，超导体和纳米线之间的界面非均匀性被强烈认为是导致无序的主要原因，也是在混合半导体-超导体系的隧道研究中普遍存在的“软超导能隙”的主要原因。此外，纳米线系统中缺乏弹道输运可能会产生类似于马约拉纳特征的束缚态。我们通过开发选择性区域外延 Al 到 InSb 纳米线的技术来解决这些问题，该技术适用于其他纳米线和超导体。外延 InSb-Al 器件通常具有硬超导能隙，并表现出弹道一维超导性和单模区中超电流的近乎完美传输，这是工程和控制一维拓扑超导性的必要条件。此外，我们还证明了使用选择性区域外延制备的基于马约拉纳的量子计算应用的基础超导岛器件外延 InSb-Al 可以实现微米级的弹道一维传输。我们的结果为开发用于量子器件应用的弹道超导电子网络铺平了道路。
