Subgap spectroscopy along hybrid nanowires by nm-thick tunnel barriers

Vukan Levajac, Ji Yin Wang*, Cristina Sfiligoj, Mathilde Lemang, Jan Cornelis Wolff, Alberto Bordin, Ghada Badawy, Sasa Gazibegovic, Erik P.A.M. Bakkers, Leo P. Kouwenhoven

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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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.

Original languageEnglish
Article number6647
Number of pages8
JournalNature Communications
Issue number1
Publication statusPublished - 2023


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