Superconducting Spintronics

这个项目将研究超导和磁性之间的协同作用，可以在某些设备中进行工程设计，并利用这一点来展示超导自旋电子学作为未来的计算技术。在铁磁金属中，内部交换场产生具有上下自旋的电子数量的不平衡，这意味着从铁磁体涌入非磁性金属的电流除了带有电荷外，还带有净自旋。这种自旋极化电流被用于逻辑和传感器应用(例如硬盘驱动器)，而找到产生和控制它们的方法是自旋电子学(自旋电子学)的主要目标。然而，用于产生自旋电流的电荷电流的热损失可能是相当大的，这是目前自旋电子学(如集成存储芯片)应用受限的原因之一。在超导体中，电荷可以在没有耗散的情况下流动，但由于库珀对由具有反平行自旋的电子组成，电荷电流不能携带自旋。此外，由于库珀对很容易被磁性破坏，超导和铁磁性的耦合可能看起来对自旋电子学的应用毫无用处。然而，在过去的几年里，一系列的发现表明，不仅可以使磁学和超导电性合作，而且在精心设计的超导体/磁体系统中，可以创造出新的功能，其中自旋、电荷和超导相干性可以一起工作。通过结合这些不同的自由度，一系列全新的最新预测正在等待实验探索。通过这个雄心勃勃的计划，我们有机会将关于超导和磁性之间相互作用的一系列预测和发现转化为一种演示技术，最终可能被开发为大规模基于半导体的逻辑的替代品。我们提出的超导自旋电子学领域的想法远远超出了消除传统自旋电子(自旋电子学)电路固有的阻性损耗的简单想法，而是旨在利用超导状态的独特属性来控制自旋电流和自旋积累。该计划汇集了来自三个不同专业的团队-超导设备、高速自旋电子学和介观物理中的强关联理论-他们将合作识别和研究支撑科学的关键。这项将从该方案中产生的基础科学将使我们能够了解许多预测的影响中哪些是长期发展可行的。方案拨款的灵活性将使我们能够在所有潜在要素上并行工作，然后逐步专注于展示设备最有希望的那些：首先是可以无限期存储数据但可以以超低能量切换的存储设备，其次是某种形式的逻辑设备。后者可以是类似晶体管的结构，也可以是为传统自旋电子学提出的全自旋逻辑器件之一。这些超导自旋电子学设备的雄心在于，它们将结合传统自旋电子学固有的可扩展性和超导体提供的高速和低功率。风险如此之大，以至于我们可能无法实现所有这些想法，但通过并行研究一系列将超导和自旋输运结合在一起的不同现象，我们有一个独特的机会来定义一个新的技术领域。

This programme will study the synergy between superconductivity and magnetism which can be engineered in certain devices and use this to demonstrate superconducting spintronics as future computing technology.In ferromagnetic metals, an internal exchange field generates an imbalance in the number of electrons with up and down spins which means that currents that emerge from ferromagnets into non-magnetic metals carry a net spin in addition to charge. Such spin polarized currents are utilized for logic and sensor applications (for example in hard disk drives), and finding ways to generate and control them is a major goal of spin electronics (spintronics). However, the heat loss from the charge currents used to generate spin currents can be considerable and this is one reason why applications of spintronics, such as integrated memory chips, are presently limited.In superconductors charge can flow without dissipation but, since the Cooper pairs consist of electrons with antiparallel spins, charge currents cannot carry spin. Further, since Cooper pairs are easily disrupted by magnetism, the coupling of superconductivity and ferromagnetism might appear useless for applications in spintronics. However, during the past few years a series of discoveries have shown that, not only can magnetism and superconductivity be made to cooperate, but in carefully engineered superconductor/magnet systems new functionality can be created in which spin, charge and superconducting phase coherence can work together. By combining these different degrees of freedom a whole new spectrum of recent predictions is waiting to be explored experimentally.Through this ambitious programme we have the chance to transform this array of predictions and discoveries about the interaction between superconductivity and magnetism into a demonstration technology which could eventually be developed as a replacement for large-scale semiconductor-based logic. Our ideas for the proposed field of superconducting spintronics go far beyond the simple ideas of eliminating resistive losses inherent in conventional spin electronic (spintronic) circuits, but instead aim to exploit unique attributes of the superconducting state to control spin currents and spin accumulation. The programme brings together teams from three different specialties - superconducting devices, high speed spintronics and theory of strong correlations in mesoscopic physics - which will work together to identify and investigate the key underpinning science. This basic science which will emerge from the programme will allow us to understand which of the many predicted effects are viable for long-term development. The flexibility of a Programme Grant will allow us to work in parallel on all the potential elements and then progressively focus on those that show most promise for demonstrator devices: firstly a memory device which can store data indefinitely but can be switched with ultra-low energy and, secondly, some form of logic device. The latter may be a transistor-like structure or one of the all-spin logic devices proposed for conventional spintronics. The ambition for these superconducting spintronic devices is that they will combine the scalability inherent in conventional spintronics and the high speed and low power offered by superconductors. The risks are such that we may not be able to realise all of these ideas but, by working in parallel on a wide range of different phenomena which couple superconductivity and spin transport, we have a unique opportunity to define a new technology field.