Boosting Transparency in Topological Josephson Junctions via Stencil Lithography

TL;DR

This paper introduces an in-situ fabrication process combining molecular beam epitaxy and stencil lithography to create high-quality topological insulator-superconductor hybrid devices with potential for topological quantum computing.

Contribution

It presents a novel in-situ fabrication method for TI-SC hybrids that achieves high interface transparency and evidence of Majorana bound states.

Findings

Nearly perfect interface transparency in Josephson junctions

Large $I_CR_N$ products observed

Presence of Majorana bound states indicated by RF measurements

Abstract

Hybrid devices comprised of topological insulator (TI) nanostructures in proximity to s-wave superconductors (SC) are expected to pave the way towards topological quantum computation. Fabrication under ultra-high vacuum conditions is necessary to attain high quality of TI-SC hybrid devices, because the physical surfaces of V-VI three-dimensional TIs suffer from degradation at ambient conditions. Here, we present an in-situ process, which allows to fabricate such hybrids by combining molecular beam epitaxy and stencil lithography. As-prepared Josephson junctions show nearly perfect interface transparency and very large $I_CR_N$ products. The Shapiro response of radio frequency measurements indicates the presence of gapless Andreev bound states, so-called Majorana bound states.