Ballistic Josephson junctions based on CVD graphene
Ballistic Josephson junctions based on CVD graphene
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DOI：
10.1088/1361-6668/aaab81
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发表时间：
2017-03
影响因子：
3.6
通讯作者：
Tianyi Li;J. Gallop;L. Hao;E. Romans
中科院分区：
文献类型：
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作者：
Tianyi Li;J. Gallop;L. Hao;E. Romans
近年来，石墨烯约瑟夫森结作为超导体之间的薄弱环节，在基础物理和潜在应用方面得到了深入研究。然而，之前的大部分工作都是基于机械剥离的石墨烯，这与晶圆规模生产不兼容。为了克服这一限制，我们使用化学气相沉积（CVD）生长的石墨烯作为约瑟夫森结的薄弱环节。我们证明，带有 Nb 电极的非常短、宽的基于 CVD 石墨烯的约瑟夫森结可以在从 1.5 K 到 320 mK 的基础温度的电特性中没有任何不良的磁滞，并且其栅极可调临界电流在垂直磁场中显示出理想的类似夫琅和费的干涉图样。此外，对于我们最短的结（长度为 50 nm），我们发现正常状态电阻随栅极电压振荡，与处于弹道状态的结一致，这是以前在基于 CVD 石墨烯的约瑟夫森结中未观察到的特征。
Josephson junctions with graphene as the weak link between superconductors have been intensely studied in recent years, with respect to both fundamental physics and potential applications. However, most of the previous work was based on mechanically exfoliated graphene, which is not compatible with wafer-scale production. To overcome this limitation, we have used graphene grown by chemical vapour deposition (CVD) as the weak link of Josephson junctions. We demonstrate that very short, wide CVD-graphene-based Josephson junctions with Nb electrodes can work without any undesirable hysteresis in their electrical characteristics from 1.5 K down to a base temperature of 320 mK, and their gate-tuneable critical current shows an ideal Fraunhofer-like interference pattern in a perpendicular magnetic field. Furthermore, for our shortest junctions (50 nm in length), we find that the normal state resistance oscillates with the gate voltage, consistent with the junctions being in the ballistic regime, a feature not previously observed in CVD-graphene-based Josephson junctions.