Transparent Josephson Junctions in Higher-Order Topological Insulator WTe2 via Pd Diffusion

Abstract

Highly transparent superconducting contacts to a topological insulator (TI) remain a persistent challenge on the route to engineer topological superconductivity. Recently, the higher-order TI WTe${}_2$ was shown to turn superconducting when placed on palladium (Pd) bottom contacts, demonstrating a promising material system in pursuing this goal. Here, we report the diffusion of Pd into WTe${}_2$ and the formation of superconducting PdTe${}_x$ as the origin of observed superconductivity. We find an atomically sharp interface in vertical direction to the van der Waals layers between the diffusion crystal and its host crystal, forming state-of-the-art superconducting contacts to a TI. The diffusion is discovered to be non-uniform along the width of the WTe${}_2$ crystal, with a greater extend along the edges compared to the bulk. The potential of this contacting method is highlighted in transport measurements on Josephson junctions by employing external superconducting leads.

As accepted to Physical Review Materials, includes main text (8 pages, 4 figures) and supplemental material (8 pages, 2 figures)

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Cited by in corpus (5)

• Current-phase relation of a WTe2 Josephson junction
• Surface-Confined Two-Dimensional Crystal Growth on a Monolayer
• Gate-defined Josephson weak-links in monolayer $\mathrm{WT}{\mathrm{e}}_2$
• Pre-Patterned Superconducting Contacts for Clean Superconductor-Topological Material Interfaces Enabling Long-Range Josephson Coupling
• Probing the topological protection of edge states in multilayer tungsten ditelluride with the superconducting proximity effect