论文标题
基于偏见的多末端石墨烯的约瑟夫森交界处，库珀四重奏的4E均值证据
Evidence for 4e charge of Cooper quartets in a biased multi-terminal graphene-based Josephson junction
论文作者
论文摘要
在约瑟夫森交界处（JJ）中，库珀对通过超导体之间的Andreev绑定状态（ABS）运输。多末端（MT）JJ的弱连接中的ABS可以在不同的超导电极之间连贯地杂交两个库珀对，从而导致涉及四个费米子纠缠的库珀四重奏（CQ）。由于AC Josephson效应，这些CQ-ABS的能量光谱可以通过偏置MT-JJ来控制。在这里，使用可调节的栅极可调节的四端石墨烯JJs辅助通量环，我们用可调频谱构造CQ。临界四重奏超电流表现出与4E电荷相关的磁振荡。从而提供了纠缠CQ-ABS之间干扰的证据。在有限的偏置电压下，我们发现DC四重奏超电流显示出非单调偏置依赖性行为，这归因于不同浮雕带之间的Landau-Zener转变。我们对连贯的非平衡CQ-ABS的实验证明为基于MT-JJ的人工拓扑材料设计的途径设定了一条途径。
In a Josephson junction (JJ), Cooper pairs are transported via Andreev bound states (ABSs) between superconductors. The ABSs in the weak link of multi-terminal (MT) JJs can coherently hybridize two Cooper pairs among different superconducting electrodes, resulting in the Cooper quartet (CQ) involving four fermions entanglement. The energy spectrum of these CQ-ABS can be controlled by biasing MT-JJs due to the AC Josephson effect. Here, using gate tunable four-terminal graphene JJs complemented with a flux loop, we construct CQs with a tunable spectrum. The critical quartet supercurrent exhibits magneto-oscillation associated with a charge of 4e; thereby presenting the evidence for interference between entangled CQ-ABS. At a finite bias voltage, we find the DC quartet supercurrent shows non-monotonic bias dependent behavior, attributed to Landau-Zener transitions between different Floquet bands. Our experimental demonstration of coherent non-equilibrium CQ-ABS sets a path for design of artificial topological materials based on MT-JJs.
