Spin-Orbit Coupling-Driven Superconducting Spintronics

铁磁性是由材料中电子自旋的平行排列引起的，比传统的单重态超导电性强得多，这是由于电子与相反的自旋配对造成的。因此，超导和铁磁性之间的耦合或邻近效应是短程的，并且仅限于两种材料界面的几个纳米范围内。然而，在过去的十年里，超导和铁磁性相互作用的惊人结果挑战了这一传统图景。在适当设计的超导体/铁磁界面上，有可能产生由相等的自旋对电子(三重态对)介导的超导电性，使超导体能够携带具有非零自旋的无耗散电流。有限的自旋极化和零耗散将基于自旋的电子学(自旋电子学)和超导电子学的丰富势整合为一个丰富的超导自旋电子学新领域。虽然在超导体/铁磁界面产生三重态对在根本上和潜在的应用上都很有吸引力，但它需要非常复杂的磁结构。引人注目的是，通过在超导体/铁磁异质结中加入自旋轨道耦合可以实现显著的简化。我们最近的实验表明，利用超导体/铁磁界面上的重金属，可以用一个简单的均匀铁磁产生和控制三重态对。这不仅从根本上简化了超导自旋电子学中使用的结构，而且为研究由于超导、铁磁和自旋轨道耦合共存而发生的一类新的效应打开了可能性。在这个建议中，我们将通过集中在三个关键领域来建立我们的理解：理解材料和界面的作用，最大化三重态的产生效率，最后，展示一个利用自旋轨道耦合来工作于三重态产生和控制的功能装置。有了这些目标，我们希望实现i)自旋-轨道耦合作为三重态的有效源和控制因素，从而使超导自旋电子学的想法在实际中可行ii)一种比以前设计的任何功能都简单得多的功能器件，并作为未来具有全新功能的器件设计的蓝图。

Ferromagnetism arises from parallel alignment of electron spins in a material and is much stronger than conventional singlet superconductivity resulting from the pairing of electrons with opposite spins. Therefore, the coupling or the proximity effect between superconductivity and ferromagnetism is short-ranged and is restricted to only a few nanometres from the interface of the two materials.However, in the last ten years surprising results from the interaction of superconductivity and ferromagnetism has challenged this conventional picture. At suitably engineered superconductor/ferromagnet interfaces, it is possible to generate superconductivity mediated by equal spin-paired electrons (triplet pairs) enabling a superconductor to carry a dissipationless current with a non-zero spin. The finite spin-polarisation and the zero dissipation integrates the rich potentials of spin based electronics (spintronics) and superconducting electronics into a rich new field of superconducting spintronics. Although attractive both fundamentally and in its reach for potential applications, generating triplet pairs at superconductor/ferromagnet interfaces require prohibitively complex magnetic structures.Strikingly, a dramatic simplification can be achieved by incorporating spin-orbit coupling in superconductor/ferromagnet heterostructures. Our recent experiments have indicated that using heavy-metals at superconductor/ferromagnet interfaces, it is possible to generate and control triplet pairs using a simple homogeneous ferromagnet. This not only radically simplifies structures used in superconducting spintronics but opens-up the possibility to study a new class of effects predicted to occur due to the coexistence of superconductivity, ferromagnetism and spin-orbit coupling.In this proposal, we will establish our understanding by focusing on three key areas: understanding the role of the materials and interfaces, maximise the triplet generation efficiency and finally, demonstrate a functional device working on triplet generation and control using spin-orbit coupling. With these objectives, we hope to achieve i) spin-orbit coupling as an efficient source and controlling factor for triplets thereby making superconducting spintronics ideas practically feasible ii) a functional device that is far simpler than any previously designed and serves as a blue-print for future device designs with radically new functionalities.