Prominent Josephson tunneling between twisted single copper oxide planes of Bi$_2$Sr$_{2-x}$LaxCuO$_{6+y}$

Heng Wang; Yuying Zhu; Zhonghua Bai; Zechao Wang; Shuxu Hu; Hong-Yi Xie; Xiaopeng Hu; Jian Cui; Miaoling Huang; Jianhao Chen; Ying Ding; Lin Zhao; Xinyan Li; Qinghua Zhang; Lin Gu; X. J. Zhou; Jing Zhu; Ding Zhang; Qi-Kun Xue

doi:10.1038/s41467-023-40525-1

arXiv · 2311.11540

Prominent Josephson tunneling between twisted single copper oxide planes of Bi$_2$Sr$_{2-x}$LaxCuO$_{6+y}$

Heng Wang·Yuying Zhu·Zhonghua Bai·Zechao Wang·Shuxu Hu·Hong-Yi Xie·Xiaopeng Hu·Jian Cui·Miaoling Huang·Jianhao Chen·Ying Ding·Lin Zhao·Xinyan Li·Qinghua Zhang·Lin Gu·X. J. Zhou·Jing Zhu·Ding Zhang·Qi-Kun Xue

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Abstract

Josephson tunneling in twisted cuprate junctions provides a litmus test for the pairing symmetry, which is fundamental for understanding the microscopic mechanism of high temperature superconductivity. This issue is rekindled by experimental advances in van der Waals stacking and the proposal of an emergent d+id-wave. So far, all experiments have been carried out on Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (Bi-2212) with double CuO$_2$ planes but show controversial results. Here, we investigate junctions made of Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+y}$ (Bi-2201) with single CuO$_2$ planes. Our on-site cold stacking technique ensures uncompromised crystalline quality and stoichiometry at the interface. Junctions with carefully calibrated twist angles around 45{\deg} show strong Josephson tunneling and conventional temperature dependence. Furthermore, we observe standard Fraunhofer diffraction patterns and integer Fiske steps in a junction with a twist angle of 45.0$\pm$0.2{\deg}. Together, these results pose strong constraints on the d or d+id-wave pairing and suggest an indispensable isotropic pairing component.

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Heng Wang, Yuying Zhu, Zhonghua Bai, Zechao Wang, Shuxu Hu, Hong-Yi Xie, Xiaopeng Hu, Jian Cui, Miaoling Huang, Jianhao Chen, Ying Ding, Lin Zhao, Xinyan Li, Qinghua Zhang, Lin Gu, X. J. Zhou, Jing Zhu, Ding Zhang, Qi-Kun Xue. 2023-11-20. Prominent Josephson tunneling between twisted single copper oxide planes of Bi$_2$Sr$_{2-x}$LaxCuO$_{6+y}$. https://doi.org/10.1038/s41467-023-40525-1

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