Correlating Josephson supercurrents and Shiba states in quantum spins unconventionally coupled to superconductors.
Correlating Josephson supercurrents and Shiba states in quantum spins unconventionally coupled to superconductors.
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DOI：
10.1038/s41467-021-21347-5
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发表时间：
2021-02-17
影响因子：
16.6
通讯作者：
Sessi P
中科院分区：
文献类型：
--
作者：
Küster F;Montero AM;Guimarães FSM;Brinker S;Lounis S;Parkin SSP;Sessi P
与超导体耦合的局域自旋引起了几种与库珀对形成和磁交换之间的竞争直接相关的新兴现象。通常使用光谱方法来检查这些效应，该方法依赖于检测库珀对断裂产生的带内束缚模式，即所谓的 Yu-Shiba-Rusinov (YSR) 态。然而，局部磁性杂质对超导有序参数的影响在很大程度上仍未得到探索。在这里，我们使用扫描约瑟夫森光谱直接可视化磁扰动对原子尺度超导电极之间库珀对隧道的影响。通过一次添加一个电子来增加磁性杂质轨道占据，我们揭示了约瑟夫森超电流抑制和 YSR 态之间存在直接相关性。此外，在金属态中，我们检测到零偏差异常，这打破了基于竞争的近藤和库珀对单线态形成机制的现有框架。基于第一性原理计算，这些结果根据有限磁各向异性能量引起的非常规自旋激发进行了合理化。我们的发现对于依赖量子自旋和超导之间相互作用的现象具有深远的影响。局部磁性杂质对超导有序参数的影响在很大程度上仍未得到探索。在这里，作者可视化了不同磁扰动对超导体的影响，揭示了不同光谱范围内量子自旋和超导性之间相互作用的丰富相关性。
Local spins coupled to superconductors give rise to several emerging phenomena directly linked to the competition between Cooper pair formation and magnetic exchange. These effects are generally scrutinized using a spectroscopic approach which relies on detecting the in-gap bound modes arising from Cooper pair breaking, the so-called Yu-Shiba-Rusinov (YSR) states. However, the impact of local magnetic impurities on the superconducting order parameter remains largely unexplored. Here, we use scanning Josephson spectroscopy to directly visualize the effect of magnetic perturbations on Cooper pair tunneling between superconducting electrodes at the atomic scale. By increasing the magnetic impurity orbital occupation by adding one electron at a time, we reveal the existence of a direct correlation between Josephson supercurrent suppression and YSR states. Moreover, in the metallic regime, we detect zero bias anomalies which break the existing framework based on competing Kondo and Cooper pair singlet formation mechanisms. Based on first-principle calculations, these results are rationalized in terms of unconventional spin-excitations induced by the finite magnetic anisotropy energy. Our findings have far reaching implications for phenomena that rely on the interplay between quantum spins and superconductivity. The impact of local magnetic impurities on superconducting order parameter remains largely unexplored. Here, the authors visualize the effect of different magnetic perturbations on a superconductor, unveiling a rich correlation of the interplay between quantum spins and superconductivity in different spectroscopic regimes.
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