Controllable 0-π Josephson junctions containing a ferromagnetic spin valve
Controllable 0-π Josephson junctions containing a ferromagnetic spin valve
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DOI：
10.1038/nphys3681
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发表时间：
2016-06-01
期刊：
影响因子：
19.6
通讯作者：
Birge, Norman O.
中科院分区：
文献类型：
--
作者：
Gingrich, E. C.;Niedzielski, Bethany M.;Birge, Norman O.
超导性和铁磁性是对立的有序形式，很少共存。然而，在混合超导/铁磁系统中出现了许多有趣的新现象。例如，包含铁磁材料的约瑟夫森结对于材料（1）的某些厚度可以在其基态表现出π的本征相移。这种“π结”在2001年首次在实验上实现（参考文献2，3），并已被提议作为高速经典超导计算和量子计算的电路元件（4-10）。在这里，我们证明实验的约瑟夫森结包含两个铁磁层的相位状态可以通过改变两个磁化的相对取向在0和π之间切换。这些可控的0-π结在低温存储器中有直接的应用，在那里它们作为超低功率超导计算机的必要组件。这种完全超导计算机估计比目前基于超导体的超级计算机（12）的能量效率高出几个数量级。相位可控结也为超导电路元件开辟了新的可能性，例如超导“可编程逻辑”，它们可以在超导模拟器中运行到现场可编程门阵列。
Superconductivity and ferromagnetism are antagonistic forms of order, and rarely coexist. Many interesting new phenomena occur, however, in hybrid superconducting/ferromagnetic systems. For example, a Josephson junction containing a ferromagnetic material can exhibit an intrinsic phase shift of pi in its ground state for certain thicknesses of the material(1). Such 'pi-junctions' were first realized experimentally in 2001 (refs 2,3), and have been proposed as circuit elements for both high-speed classical superconducting computing and for quantum computing(4-10). Here we demonstrate experimentally that the phase state of a Josephson junction containing two ferromagnetic layers can be toggled between 0 and pi by changing the relative orientation of the two magnetizations. These controllable 0-pi junctions have immediate applications in cryogenic memory, where they serve as a necessary component to an ultralow power superconducting computer(11). Such a fully superconducting computer is estimated to be orders of magnitude more energy-efficient than current semiconductor-based supercomputers(12). Phase-controllable junctions also open up new possibilities for superconducting circuit elements such as superconducting 'programmable logic', where they could function in superconducting analogues to field-programmable gate arrays.