Strong Proximity Josephson Coupling in Vertically Stacked NbSe<sub>2</sub>-Graphene-NbSe<sub>2</sub> van der Waals Junctions.
basic_science · Level V
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- Record sourced from PubMed, PMID 28952735.
- Also identified by DOI 10.1021/acs.nanolett.7b02707.
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Abstract
A layered two-dimensional superconducting material 2H-NbSe<sub>2</sub> is used to build a van der Waals heterostructure, where a proximity-coupled superconducting order can be induced in the interfacing materials. Vertically stacked NbSe<sub>2</sub>-graphene-NbSe<sub>2</sub> is fabricated using van der Waals interlayer coupling, producing defect-free contacts with a high interfacial transparency. The atomically thin graphene layer allows the formation of a highly coherent proximity Josephson coupling between the two NbSe<sub>2</sub> flakes. The temperature dependence of the junction critical current (I<sub>c</sub>) reveals short and ballistic Josephson coupling characteristics that agree with theoretical prediction. The strong Josephson coupling is confirmed by a large junction critical current density of 1.6 × 10<sup>4</sup> A/cm<sup>2</sup>, multiple Andreev reflections in the subgap structure of the differential conductance, and a magnetic-field modulation of I<sub>c</sub>. This is the first demonstration of strongly proximity-coupled Josephson junctions with extremely clean interfaces in a dry-transfer-stacked van der Waals heterostructure.