Long-range superconducting proximity effect in nickel nanowires
Long-range superconducting proximity effect in nickel nanowires
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DOI：
10.1103/physrevresearch.4.023133
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发表时间：
2021-07
影响因子：
4.2
通讯作者：
Jue Jiang;Weiwei Zhao;Fei Wang;R. Du;L. Miao;Ke Wang;Qi Li;Cui-Zu Chang;M. Chan
中科院分区：
文献类型：
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作者：
Jue Jiang;Weiwei Zhao;Fei Wang;R. Du;L. Miao;Ke Wang;Qi Li;Cui-Zu Chang;M. Chan
当铁磁体与超导体接触时，由于不相容的自旋顺序，来自超导体的库珀对在铁磁体内部不能存活超过一到两纳米。这在与超导铌（Nb）引线接触的铁磁性镍（Ni）纳米线的测量中得到证实。然而，当在Nb电极和Ni线之间插入一层3nm厚的氧化铜缓冲层（CuO）时，超导接近范围的空间范围从2纳米急剧增加到几十纳米。扫描透射电镜研究证实，当蒸发的Cu膜暴露于空气中时，会形成3nm厚的CuO层。在SiO2/Si衬底和Nb/SiO2/Si衬底上对这种3nm的CuO薄膜进行磁化测量，显示出铁磁性的明显证据。理解Ni纳米线中远距离接近效应的一种方法是，具有铁磁性的CuO缓冲层有助于沿Ni纳米线将Nb中的单线态超导转化为三重态超电流。
When a ferromagnet is placed in contact with a superconductor, owing to incompatible spin order, the Cooper pairs from the superconductor cannot survive more than one or two nanometers inside the ferromagnet. This is confirmed in the measurements of ferromagnetic nickel (Ni) nanowires contacted by superconducting niobium (Nb) leads. However, when a 3 nm thick copper oxide (CuO) buffer layer made by exposing an evaporated or a sputtered 3 nm Cu film to air, is inserted between the Nb electrodes and the Ni wire, the spatial extent of the superconducting proximity range is dramatically increased from 2 to a few tens of nanometers. Scanning transmission electron microscope study confirms the formation of a 3 nm thick CuO layer when an evaporated Cu film is exposed to air. Magnetization measurements of such a 3 nm CuO film on a SiO2/Si substrate and on Nb/SiO2/Si show clear evidence of ferromagnetism. One way to understand the long-range proximity effect in the Ni nanowire is that the CuO buffer layer with ferromagnetism facilitates the conversion of singlet superconductivity in Nb into triplet supercurrent along the Ni nanowires.