van der Waals π Josephson Junctions,Nano Letters

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van der Waals π Josephson Junctions
Nano Letters ( IF 9.6 ) Pub Date : 2022-06-23 , DOI: 10.1021/acs.nanolett.2c01640
Kaifei Kang ₁ , Helmuth Berger ₂ , Kenji Watanabe ₃ , Takashi Taniguchi ₃ , László Forró _{2,

4} , Jie Shan _{1,

5,

6} , Kin Fai Mak _{1,

5,

6}

Affiliation

Proximity-induced superconductivity in a ferromagnet can induce Cooper pairs with a finite center-of-mass momentum and stabilize Josephson junctions (JJs) with π phase difference in superconductor-ferromagnet-superconductor heterostructures. The emergence of two-dimensional layered superconducting and magnetic materials promises a new platform for realizing π JJs with atomically sharp interfaces. Here we demonstrate a thickness-driven 0-π transition in JJs made of NbSe₂ (an Ising superconductor) and Cr₂Ge₂Te₆ (a ferromagnetic semiconductor). By systematically increasing the Cr₂Ge₂Te₆ weak link thickness, we observe a vanishing supercurrent at a critical thickness of ∼8 nm, followed by a re-entrant supercurrent. Near the critical thickness, we further observe unusual supercurrent interference patterns with vanishing critical current around zero in-plane magnetic field. They signify the formation of 0-π JJs (with both 0 and π regions), likely induced by the nanoscale magnetic domains in Cr₂Ge₂Te₆.

中文翻译：

范德华 π 约瑟夫森结

铁磁体中的邻近诱导超导性可以诱导具有有限质心动量的库珀对，并稳定超导体-铁磁体-超导体异质结构中具有 π 相位差的约瑟夫森结 (JJ)。二维层状超导和磁性材料的出现为实现具有原子尖锐界面的 π JJ 提供了一个新平台。在这里，我们展示了由 NbSe ₂（一种伊辛超导体）和 Cr ₂ Ge ₂ Te ₆（一种铁磁半导体）制成的 JJ 中的厚度驱动的 0-π 跃迁。通过系统地增加 Cr ₂ Ge ₂ Te ₆弱链接厚度，我们观察到在约 8 nm 的临界厚度处消失的超电流，然后是重入超电流。在临界厚度附近，我们进一步观察到异常的超电流干涉模式，临界电流在零平面内磁场附近消失。它们表示 0-π JJs（具有 0 和 π 区域）的形成，可能是由 Cr ₂ Ge ₂ Te ₆中的纳米级磁畴引起的。

更新日期：2022-06-23

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