Integrating Superconducting and Spintronics Devices for Low-Power and High-Speed Operation and Brain-Inspired Computing

人们越来越需要解决未来计算机技术中的功耗问题，而不是继续增加一些缩小的晶体管的传统方法。超导电子学提供了前景看好的节能替代方案，即使在计入冷却成本之后也是如此。超导电子学的关键元素是约瑟夫森结，1973年诺贝尔物理学奖认可了这一点。在这个结中，两个超导体被非超导区域隔开，但零阻充电电流仍然可以流经整个器件。然而，缺乏合适的存储器仍然是一个关键挑战，阻碍了超导逻辑和存储器的整合。为了克服这一限制并释放大脑启发计算的潜力，有人建议整合自旋电子学领域的进展，在自旋电子学领域，信息由电子自旋及其替代物--磁化方向来表示。铁或钴等铁磁体的磁化强度是有限的，这是由于自旋不平衡造成的：不同数量的电子自旋与磁化轴取向不同。这是记忆的理想之选，这种磁化可以在没有电源的情况下持续存在，就像磁铁被吸引到冰箱上一样。与磁铁不同，普通超导体具有自旋平衡，它们的特征是一对自旋方向相反的电子的集合。把自旋不平衡的磁铁放在超导体旁边会破坏自旋平衡和超导电性。这项拟议的研究表明，通过工程上的自旋-轨道耦合，可以将超导体转变为具有相同自旋的成对电子，从而确保它们与磁体共存，从而将记忆与逻辑结合起来。拟议研究的结果将与外联工作密切结合起来，承认绝大多数公立学校的学生很少或根本没有接触到物理科学，这对随后的STEM学科招生产生了不利影响。将组织夏季研讨会：磁学和超导的应用，涵盖自旋电子学、电机、医学成像、磁悬浮列车和生物磁学等主题。作为一年一度的SPIE：光学和光子学会议的一部分，超导自旋电子学研讨会将被组织起来，以弥合自旋电子学和超导应用之间的差距。约瑟夫森结的标志是与相应的电流-相位关系的相位一致性，其中即使在零偏压下也可以流动无耗散电荷电流。约瑟夫森结的动力学操作类似于有阻尼单摆的振动。超快振荡，类似于钟摆的全周自转，可以在~1ps时快速切换，每个开关只耗散0.1AJ，同时产生以1/3光速传播的电流脉冲。这项拟议的工作揭示了这些性质如何能够实现潜在的变革性自旋电子器件，其中自旋-轨道耦合和磁区的存在将改变无耗散电流，从而也携带自旋并提供逻辑和存储器的无缝集成。因此，这种约瑟夫森结既可用作逻辑元件，也可用作存储器的元件：逻辑是通过超快电流脉冲实现的，而存储器是通过基于超导相的读出的磁化取向来编码的。具有自旋轨道耦合的电流-相位关系的可调性也为依赖于相控电流脉冲的大脑启发计算和人工神经网络提供了未知的机会。约瑟夫森结器件将通过对其超导和磁性的全面建模来检验，而自旋-轨道耦合的精确形式将从第一原理原子研究中计算出来。这些结果将通过与制造约瑟夫森结的几个小组的合作进行实验验证。拟议研究的结果将与外联工作密切结合起来，承认绝大多数公立学校的学生很少或根本没有接触到物理科学，这对随后的STEM学科招生产生了不利影响。国际和平协会将组织夏季研讨会：磁学和超导的应用，涵盖自旋电子学、电机、医学成像、磁悬浮列车和生物磁学等主题。作为一年一度的SPIE：光学+光子学会议的一部分，PI将组织超导自旋电子学研讨会，以弥合自旋电子学和超导应用之间的差距。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

There is a growing need to address the power consumption in future computer technologies, beyond the traditional approach of a continued increase in a number of scaled-down transistors. Superconducting electronics offers promising energy-efficient alternatives, even after including the cost of cooling. The key element of superconducting electronics is the Josephson junction, recognized by the 1973 Nobel Prize in Physics. In this junction two superconductors are separated by the nonsuperconducting region, but zero-resistance charge current can still flow across the whole device. However, the lack of suitable memories remains a key challenge and prevents the integration of superconducting logic and memory. To overcome this limitation and unlock potential for brain-inspired computing, it is proposed to integrate advances from the field of spintronics where information is represented by electron spin and by its proxy, the direction of magnetization. Ferromagnets such as iron or cobalt have a finite magnetization, resulting from a spin imbalance: a different number of electron spins is oriented with or against the magnetization axis. Ideal for memory, this magnetization persists without an outlet power, just as the magnet is attracted to the fridge. Unlike magnets, common superconductors have spin balance, they are characterized by a collection of paired electros with spins of opposite directions. Bringing a magnet with its spin imbalance next to a superconductor destroys the spin balance and superconductivity. The proposed research reveals that by engineering spin-orbit coupling it is possible to transform superconductors to have paired electrons of equal spins thereby ensuring their coexistence with magnets for integrating memory with logic. The findings of the proposed research will be closely integrated with the outreach efforts, recognizing that a vast majority of public-school students have minimal or no exposure to physical sciences adversely affecting the subsequent enrolment in STEM disciplines. Summer Workshops will be organized on: Applications of Magnetism and Super-conductivity covering topics on spintronics, motors, medical imaging, Maglev trains, and biomagnetism. As a part of the annual SPIE: Optics&Photonics Conference, Superconducting Spintronics Symposia will be organized to bridge the gap between the spintronics and superconducting applications.The hallmark of Josephson junctions is the phase-coherence with the corresponding current-phase relations, where dissipationless charge current can flow even at zero applied bias. Dynamical operation of Josephson junctions resembles oscillations of a damped pendulum. Ultrafast oscillations, analogous to the full-circle rotation of a pendulum, can be switched quickly at ~1 ps, dissipate only 0.1 aJ per switch, while producing current pulses that travel at 1/3 of the speed of light. The proposed work reveals how these properties can enable potentially transformative spintronic devices in which the presence of spin-orbit coupling and magnetic regions would alter dissipationless currents to also carry spin and provide a seamless integration of logic and memory. Such Josephson junctions therefore serve both as an element of logic and of memory: logic is implemented through ultrafast current pulses, while the memory is encoded through the magnetization orientation with the readout based on the superconducting phase. The tunability of current-phase relations with spin-orbit coupling also offers unexplored opportunities in brain-inspired computing and artificial neural networks, relying on phase-controlled current pulses. Josephson junction devices will be examined through comprehensive modeling of their superconducting and magnetic properties, while the precise form of spin-orbit coupling will be calculated from the first-principles atomistic studies. These results will be experimentally verified through collaborations with several groups fabricating Josephson junctions. The findings of the proposed research will be closely integrated with the outreach efforts, recognizing that a vast majority of public-school students have minimal or no exposure to physical sciences adversely affecting the subsequent enrolment in STEM disciplines. The PI will organize Summer Workshops: Applications of Magnetism and Super-conductivity covering topics on spintronics, motors, medical imaging, Maglev trains, and biomagnetism. As a part of the annual SPIE: Optics+Photonics Conference, the PI will organize Superconducting Spintronics Symposia to bridge the gap between the spintronics and superconducting applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.