Prepatterned Superconducting Contacts for Clean Superconductor-Topological Material Interfaces Enabling Long-Range Josephson Coupling.

Choi, Yong-Bin; Choi, Chang-Won; Holtzman, Luke; Kim, Hoil; Kang, Seongwoo; Watanabe, Kenji; Taniguchi, Takashi; Hone, James et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Phase-coherent superconducting proximity in topological materials (TMs) requires clean superconductor-topological material (SC-TM) interfaces, yet conventional top-contact fabrication often degrades them through oxidation, polymer residue, and process-induced disorder. Here we introduce a prepatterned superconducting bottom-contact architecture in which MoRe/Au electrodes are defined before van der Waals (vdW) crystal transfer, thereby avoiding on-flake lithography after transfer. In WTe<sub>2</sub>- and Bi<sub>1.5</sub>Sb<sub>0.5</sub>Te<sub>1.7</sub>Se<sub>1.3</sub>-based Josephson junctions, this architecture yields systematically larger <i>I</i><sub>c</sub><i>R</i><sub>N</sub> and longer-ranged coupling than conventional top contacts. Cross-sectional scanning transmission electron microscopy/energy-dispersive spectroscopy reveals atomically abrupt, chemically well-separated interfaces. These results establish prepatterned SC-TM contacts as a practical route to reproducible, micrometer-scale Josephson platforms in vdW TMs.