Department of Condensed Matter Physics, Braun Center for Submicron Research, Weizmann Institute of Science, 76100 Rehovot, Israel.
Department of Condensed Matter Physics, Braun Center for Submicron Research, Weizmann Institute of Science, 76100 Rehovot, Israel;
Proc Natl Acad Sci U S A. 2018 Jul 3;115(27):6991-6994. doi: 10.1073/pnas.1800044115. Epub 2018 Jun 18.
A novel nonlocal supercurrent, carried by quartets, each consisting of four electrons, is expected to appear in a voltage-biased three-terminal Josephson junction. This supercurrent results from a nonlocal Andreev bound state (ABS), formed among three superconducting terminals. While in a two-terminal Josephson junction the usual ABS, and thus the dc Josephson current, exists only in equilibrium, the ABS, which gives rise to the quartet supercurrent, persists in the nonlinear regime. In this work, we report such resonance in a highly coherent three-terminal Josephson junction made in an InAs nanowire in proximity to an aluminum superconductor. In addition to nonlocal conductance measurements, cross-correlation measurements of current fluctuations provided a distinctive signature of the quartet supercurrent. Multiple device geometries had been tested, allowing us to rule out competing mechanisms and to establish the underlying microscopic origin of this coherent nondissipative current.
一种新的非局域超导电流有望出现在带电压的三端约瑟夫森结中，这种超导电流由由四个电子组成的四重态携带，四重态是由三个超导结形成的非局域安德烈夫束缚态。在二端约瑟夫森结中，通常的安德烈夫束缚态（ABS）和直流约瑟夫森电流仅在平衡状态下存在，而产生四重态超导电流的 ABS 则存在于非线性区域。在这项工作中，我们在靠近铝超导体的 InAs 纳米线中制作的高度相干三端约瑟夫森结中报告了这种共振。除了非局域电导测量外，电流波动的互相关测量也提供了四重超导电流的独特特征。我们测试了多种器件结构，排除了竞争机制，并确定了这种相干非耗散电流的潜在微观起源。
