Lee Gil-Ho, Kim Sol, Jhi Seung-Hoon, Lee Hu-Jong
1] Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea [2].
Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
Nat Commun. 2015 Jan 30;6:6181. 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.
为了实现包含各种材料的混合约瑟夫森结，以便对奇异物理现象进行基础研究以及应用于超导量子器件，人们已经付出了很多努力。尽管如此，这些努力一直受到导电通道和界面的扩散性质的阻碍。为了克服这些障碍，我们在超导电极之间垂直夹入了一层劈开的石墨烯单原子层作为正常导电间隔层。原子级薄的单晶石墨烯层充当了最终的短导电通道，与超导体具有高度透明的界面。特别是，我们展示了强约瑟夫森耦合达到理论极限、约瑟夫森临界电流的凸形温度依赖性以及约瑟夫森电流异常倾斜的相位依赖性；所有这些都证明了真正的短程和弹道约瑟夫森性质。这种用于极薄透明间隔层的垂直堆叠方案将为探索原子尺度上发生的奇异相干现象开辟一条新途径。
