Using double quantum dots as the weak link of a Josephson junction, we realize the superconducting analog of the celebrated two-impurity Kondo model. The device shows a cusped current-voltage characteristic, which can be modeled by an overdamped circuit relating the observed cusp current to the Josephson critical current. The gate dependence of the cusp current and of the subgap spectra are used as complementary ground-state indicators to demonstrate gate-tuned changes of the ground state from an interdot singlet to independently screened Yu-Shiba-Rusinov (YSR) singlets. In contrast to the two-impurity Kondo effect in normal-state systems, the crossover between these two singlets is heralded by quantum phase boundaries to nearby doublet YSR phases in which only a single spin is screened.

中文翻译：

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耦合量子点中的两个杂质的Yu-Shiba-Rusinov态

使用双量子点作为约瑟夫森结的弱链接，我们实现了著名的两杂质近藤模型的超导类似物。该设备显示了尖峰电流-电压特性，可以通过将观察到的尖峰电流与约瑟夫森临界电流相关联的过阻尼电路来建模。尖峰电流和子带隙频谱的门相关性用作补充的基态指示剂，以说明门态从点间单峰到独立筛选的Yu-Shiba-Rusinov（YSR）单峰的门调谐变化。与正常状态系统中的两个杂质近藤效应相反，这两个单峰之间的交叉被量子相边界预示为附近的双峰YSR相，其中仅筛选了一个自旋。