Superconducting Spintronics

该计划将研究超导性和磁性之间的协同作用，并将其用于演示超导自旋电子学作为未来的计算技术。在铁磁金属中，内部交换场产生上下自旋电子数量的不平衡，这意味着从铁磁体进入非磁性金属的电流除了携带电荷外，还携带净自旋。这种自旋极化电流用于逻辑和传感器应用（例如在硬盘驱动器中），并且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，这就是为什么自旋电子学的应用，如集成存储器芯片，目前受到限制的原因之一。在超导体中，电荷可以流动而不耗散，但是，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，超导性和铁磁性的耦合对于自旋电子学的应用可能显得毫无用处。然而，在过去的几年里，一系列的发现表明，不仅可以使磁性和超导性合作，而且在精心设计的超导体/磁体系统中，可以创造新的功能，其中自旋，电荷和超导相位相干性可以一起工作。通过结合这些不同的自由度，一个全新的近期预测谱正等待着实验探索。通过这个雄心勃勃的计划，我们有机会将这一系列关于超导性和磁性之间相互作用的预测和发现转化为一种演示技术，最终可以发展成为大规模基于磁阻的逻辑的替代品。我们对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）电路中固有的电阻损耗的简单想法，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学中的强相关理论-这将共同努力，以确定和研究关键的基础科学。这项计划将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对长期发展是可行的。计划拨款的灵活性将使我们能够并行研究所有潜在的元素，然后逐步专注于那些最有希望成为演示设备的元素：首先是可以无限存储数据但可以用超低能量切换的存储设备，其次是某种形式的逻辑设备。后者可以是晶体管结构或为传统自旋电子学提出的全自旋逻辑器件之一。这些超导自旋电子器件的目标是，它们将联合收割机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。风险是这样的，我们可能无法实现所有这些想法，但是，通过并行研究超导性和自旋输运耦合的各种不同现象，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.