Persistent Josephson tunneling between <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Bi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>CaCu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>8</mml:mn><mml:mo>+</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> flakes twisted by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mn>45</mml:mn><mml:mo>∘</mml:mo></mml:msup></mml:math> across the superconducting dome
Yuying Zhu, Heng Wang, Zechao Wang, Shuxu Hu, Genda Gu, Jing Zhu, Ding Zhang, Qi‐Kun Xue
Abstract
There is an on-going debate on the pairing symmetry -- whether it is $s$-, $d$-, or $d+i\phantom{\rule{0}{0ex}}d$-wave -- in twisted cuprates. Here, the authors obtain strong Josephson tunneling in 45${}^{\ensuremath{\circ}}$-twisted cuprates with ultrahigh interfacial quality and precisely calibrated twist angles. The results firmly establish the existence of isotropic pairing in twisted cuprates, posing strong constraints on the theory considering a pure $d$ wave or $d+i\phantom{\rule{0}{0ex}}d$ wave. They also extend the study to the overdoped regime and observe the Josephson diode effect, promising next-generation high-temperature superconducting devices.