Ultimately short ballistic vertical graphene Josephson junctions

• Published in: Nature communications 2015-01, Vol.6 (1), p.6181-6181, Article 6181
• Main Authors: Lee, Gil-Ho, Kim, Sol, Jhi, Seung-Hoon, Lee, Hu-Jong
• Format: Article
• Language: English
• Subjects: 639/766/25; 639/925/918; 639/925/927/1064; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms7181

Much efforts have been made for the realization of hybrid Josephson junctions incorporating various materials for the fundamental studies of exotic physical phenomena as well as the applications to superconducting quantum devices. Nonetheless, the efforts have been hindered by the diffusive nature of the conducting channels and interfaces. To overcome the obstacles, we vertically sandwiched a cleaved graphene monoatomic layer as the normal-conducting spacer between superconducting electrodes. The atomically thin single-crystalline graphene layer serves as an ultimately short conducting channel, with highly transparent interfaces with superconductors. In particular, we show the strong Josephson coupling reaching the theoretical limit, the convex-shaped temperature dependence of the Josephson critical current and the exceptionally skewed phase dependence of the Josephson current; all demonstrate the bona fide short and ballistic Josephson nature. This vertical stacking scheme for extremely thin transparent spacers would open a new pathway for exploring the exotic coherence phenomena occurring on an atomic scale. The functionality of Josephson junctions—a thin insulating layer between two superconducting regions—is greatly enhanced by using hybrid material systems. Here, the authors incorporate graphene into a Josephson junction and demonstrate ballistic transport through the atom-thick layer.