The Josephson effect is a prominent phenomenon of quantum supercurrents that has been widely studied in superconductors and superfluids. Typical Josephson junctions consist of two real-space superconductors (superfluids) coupled through a weak tunneling barrier. Here we propose a momentum-space Josephson junction in a spin-orbit coupled Bose-Einstein condensate, where states with two different momenta are coupled through Raman-assisted tunneling. We show that Josephson currents can be induced not only by applying the equivalent of “voltages,” but also by tuning tunneling phases. Such tunneling-phase-driven Josephson junctions in momentum space are characterized through both full mean field analysis and a concise two-level model, demonstrating the important role of interactions between atoms. Our scheme provides a platform for experimentally realizing momentum-space Josephson junctions and exploring their applications in quantum-mechanical circuits.

中文翻译：

---

动量空间约瑟夫森效应

约瑟夫森效应是量子超电流的一种突出现象，已在超导体和超流体中进行了广泛研究。典型的约瑟夫森结由两个通过弱隧道势垒耦合的实空间超导体（超流体）组成。在这里，我们提出了在自旋轨道耦合的玻色-爱因斯坦凝聚物中的动量空间约瑟夫森结，其中具有两个不同动量的状态通过拉曼辅助隧穿耦合。我们表明，不仅可以通过施加等效的“电压”来感应约瑟夫森电流，还可以通过调整隧道相位来感应约瑟夫森电流。这样的隧道相位驱动的约瑟夫森结动量空间中的原子通过完全均值场分析和简洁的两级模型来表征，证明了原子之间相互作用的重要作用。我们的方案为实验性地实现动量空间约瑟夫森结并探索其在量子力学电路中的应用提供了一个平台。