Bhatia Ekta, Srivastava Anand, Devine-Stoneman James, Stelmashenko Nadia A, Barber Zoe H, Robinson Jason W A, Senapati Kartik
School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar, Odisha 752050, India.
Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
Nano Lett. 2021 Apr 14;21(7):3092-3097. doi: 10.1021/acs.nanolett.1c00273. Epub 2021 Mar 16.
Spin-singlet Cooper pairs convert to spin-triplet Cooper pairs on passing through a magnetically noncollinear structure at a superconductor(S)/ferromagnet(F) interface. In this context, the generation of triplet supercurrents through intrinsic ferromagnetic domain walls, which are naturally occurring noncollinear magnetic features, was proposed theoretically in the past decade. However, an experimental demonstration has been lacking in the literature, particularly because of the difficulty in accessing a single domain wall, which is typically buried between two domains in a ferromagnetic material. By patterning a ferromagnetic nanoconstriction, we have been able to realize a nanoscale S/F/S planar junction, where a single domain wall (pinned at the nanoconstriction) acts as a Josephson barrier. In this geometry, we are able to show the predicted long-range triplet supercurrent across a ferromagnetic barrier exceeding 70 nm. Using this technique, we have demonstrated a ferromagnetic planar nano-SQUID device consisting of two Nb/Ni/Nb spin-triplet Josephson junctions.
自旋单重态库珀对在穿过超导体（S）/铁磁体（F）界面处的磁性非共线结构时会转变为自旋三重态库珀对。在此背景下，过去十年从理论上提出了通过本征铁磁畴壁（自然存在的非共线磁性特征）产生三重态超电流。然而，文献中一直缺乏实验证明，特别是因为难以接触到单个畴壁，单个畴壁通常埋在铁磁材料的两个畴之间。通过对铁磁纳米缩颈进行图案化处理，我们得以实现一个纳米级S/F/S平面结，其中单个畴壁（钉扎在纳米缩颈处）充当约瑟夫森势垒。在这种几何结构中，我们能够展示出预测的跨越超过70纳米铁磁势垒的长程三重态超电流。利用这项技术，我们展示了一种由两个Nb/Ni/Nb自旋三重态约瑟夫森结组成的铁磁平面纳米超导量子干涉装置。
