In a Josephson junction between two exciton condensates, the tunneling of charge-neutral electron-hole pairs has gained primary attention in the form of a supercurrent, which otherwise is challenging to detect experimentally. Here we design excitonic Josephson junctions based on graphene heterostructures that allow us to selectively sustain charge-neutral or charged supercurrent, offering unprecedented opportunities for revealing exotic physics of exciton condensates. In our schemes, each exciton condensate consists of a graphene monolayer vertically coupled with another graphene monolayer (GML), bilayer, or trilayer, shown to have characteristically different quantum phase transition temperatures. When two such identical condensates are connected, a neutral supercurrent always dominates within the GML/GML scheme, while in the other two schemes, a carrier-density induced transition can take place between the neutral and charged supercurrents. More strikingly, in the charged regime, both the electron or hole dominance and the DC or AC nature can be tuned by the chemical potential differences of the junction. These findings are also expected to be applicable to excitonic Josephson junctions beyond the graphene-based architecture.

中文翻译：

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在基于石墨烯异质结构的激子约瑟夫森结中维持电荷中性或带电超电流

在两个激子凝聚体之间的约瑟夫森结中，电荷-中性电子-空穴对的隧穿以超电流的形式获得了主要关注，否则很难通过实验检测。在这里，我们设计了基于石墨烯异质结构的激子约瑟夫森结，使我们能够选择性地维持电荷中性或带电超电流，为揭示激子凝聚物的奇异物理提供了前所未有的机会。在我们的方案中，每个激子凝聚物由一个石墨烯单层与另一个石墨烯单层 (GML)、双层或三层垂直耦合组成，显示具有不同的量子相变温度。当两个相同的冷凝物连接时，中性超电流总是在 GML/GML 方案中占主导地位，而在其他两个方案中，中性和带电超电流之间可以发生载流子密度诱导的跃迁。更引人注目的是，在带电状态下，电子或空穴的优势以及 DC 或 AC 性质都可以通过结的化学势差进行调整。这些发现也有望适用于基于石墨烯的架构之外的激子约瑟夫森结。