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

在未来的计算机技术中，越来越需要解决功耗问题，而不仅仅是持续增加数量的按比例缩小的晶体管的传统方法。超导电子产品提供了有前途的节能替代品，即使在包括冷却成本之后。超导电子学的关键元件是约瑟夫森结，获得1973年诺贝尔物理学奖。在这个结中，两个超导体被非超导区隔开，但零电阻充电电流仍然可以流过整个装置。然而，缺乏合适的存储器仍然是一个关键的挑战，并阻止超导逻辑和存储器的集成。为了克服这一限制并释放大脑启发计算的潜力，建议整合自旋电子学领域的进展，其中信息由电子自旋及其代理，磁化方向表示。铁或钴等铁磁体具有有限的磁化强度，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方向一致或相反。理想的记忆，这种磁化持续没有插座电源，就像磁铁被吸引到冰箱。与磁体不同，普通超导体具有自旋平衡，它们的特征在于具有相反方向自旋的成对电子的集合。将一个自旋不平衡的磁体放在超导体旁边，会破坏自旋平衡和超导性。拟议的研究表明，通过工程自旋轨道耦合，有可能将超导体转变为具有相等自旋的成对电子，从而确保它们与磁体共存，以将存储器与逻辑集成。拟议研究的结果将与外联工作密切结合，认识到绝大多数公立学校学生很少或根本没有接触物理科学，这对随后的STEM学科入学产生了不利影响。夏季研讨会将组织：磁性和超导性的应用，涵盖自旋电子学，电机，医学成像，磁悬浮列车和生物磁性的主题。超导自旋电子学研讨会是SPIE光学光子学年会的一部分，旨在弥合自旋电子学和超导应用之间的差距。约瑟夫森结的特点是相位相干，具有相应的电流-相位关系，即使在零偏置下也可以流动无耗散的电荷电流。约瑟夫森结的动力学操作类似于阻尼摆的振荡。超快振荡，类似于钟摆的整圈旋转，可以在约1 ps的速度下快速切换，每个开关仅消耗0.1 aJ，同时产生以1/3光速传播的电流脉冲。拟议的工作揭示了这些特性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性区域的存在将改变无耗散电流，使其也携带自旋，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以作为逻辑元件，也可以作为存储器元件：逻辑通过超快电流脉冲实现，而存储器则通过磁化方向进行编码，读出基于超导相位。电流-相位关系与自旋-轨道耦合的可调谐性也为脑启发计算和人工神经网络提供了未开发的机会，依赖于相位控制的电流脉冲。约瑟夫森结器件将通过其超导和磁性的综合建模进行检查，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。这些结果将通过与几个小组合作制造约瑟夫森结进行实验验证。拟议研究的结果将与外联工作密切结合，认识到绝大多数公立学校学生很少或根本没有接触物理科学，这对随后的STEM学科入学产生了不利影响。PI将组织夏季研讨会：磁性和超导性的应用，涵盖自旋电子学，电机，医学成像，磁悬浮列车和生物磁性的主题。作为年度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知识价值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.