Symmetry-protected spin dynamics in ferroelectric spin device

摘要：为了提高微电子系统的计算能力，在器件小型化、非基于电荷的逻辑运算和利用非冯·诺伊曼结构等多种策略中，利用电子自旋进行计算被认为是一种很有前途的解决方案。自旋器件，如自旋场效应晶体管，被认为有潜力显著提高计算性能，甚至改变当前的计算范式。在自旋器件中，电子自旋的控制——一个计算过程——是通过在宿主半导体中电场诱导的有效磁场来实现的。在大多数半导体中，磁场是多向的，因此电子自旋进动的相干控制一直是一个挑战。在这个项目中，PI将通过开发提供单向磁场的材料/设备系统来解决这个问题。在所提出的系统中，电场源于铁电极化，单向磁场是所提出系统独特对称性的自然结果。非挥发性电场和单向磁场将使所提出的自旋器件在自旋控制和功耗方面具有优势。该奖项支持理解铁电自旋器件中对称-自旋动力学关系的基础研究。从这个项目中获得的基础知识将有助于实现技术上实用的自旋场效应晶体管。因此，该奖项的成果将通过推动微电子领域的技术进步而有益于美国经济。该奖项还将促进代表性不足群体的工程教育和研究培训。技术摘要：本项目的研究目的是了解对称性和持续自旋螺旋对自旋电子器件中具有强自旋-轨道耦合的铁电半导体自旋动力学的作用。强自旋-轨道耦合在增强自旋进动导致短通道运行的同时，也抑制了可控自旋输运。这种困境一直是自旋场效应晶体管等实用自旋电子器件实现的主要障碍。在本项目中，PI希望通过选择具有强自旋-轨道耦合对称性的半导体铁电材料，在改变铁电极化的情况下，通过持续的自旋螺旋和可切换的自旋织构，实现对称保护的远程相干自旋输运。为了实现这些目标，PI将开发具有强自旋轨道耦合的高质量单晶铁电半导体，并制造铁电自旋阀和场效应晶体管。PI将研究模型材料中的自旋极化带结构和持续自旋螺旋。π将揭示铁电自旋阀和场效应晶体管的自旋寿命和自旋扩散长度。该项目还将研究铁电畴结构的动力学以及铁电畴取向对持续自旋螺旋、自旋动力学、自旋操作和扩散的影响。这项工作将推进解决具有强自旋-轨道相互作用的自旋电子系统中精确操纵和有效保存自旋之间的内在困境问题所需的基础知识。该奖项反映了美国国家科学基金会的法定使命，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。

Award Title:Symmetry-protected spin dynamics in ferroelectric spin device (Proposal ID: 2031692)Non-technical Abstract:To boost the computing power of microelectronic systems, among many strategies such as device miniaturization, using non-charge-based logic operation and harnessing non-von Neumann architectures, computing with electron spin has been proposed as a promising solution. Spin devices such as spin field effect transistor are considered to have the potential to significantly advance computing performance and even transform current computing paradigms. In spin devices, control of electron spin – a computing process – is achieved by electric field-induced effective magnetic field in the hosting semiconductor. In most semiconductors, the magnetic field is multi-directional so coherent control of electron spin precession has been a challenge. In this project, the PI will address this issue by developing material/device systems that provide unidirectional magnetic field. In the proposed system, electric field stems from ferroelectric polarization and unidirectional magnetic field is a natural consequence of the unique symmetry of the proposed system. The nonvolatile electric field and the unidirectional magnetic field will make the proposed spin devices excel in spin control and power consumption. This award supports the fundamental research of understanding symmetry-spin dynamics relation in ferroelectric spin devices. The basic knowledge obtained from this project would help the realization of technologically practical spin field effect transistors. The results from this award will therefore benefit the U.S. economy by advancing technological progresses in the field of microelectronics. The award will also promote engineering education and research training of underrepresented groups. Technical Abstract:The research objective of this project is to understand the role of symmetry and the persistent spin helix on the spin dynamics in ferroelectric semiconductors with strong spin-orbit coupling for spintronic devices. While strong spin-orbit coupling enhances spin precession leading to short channel operation, it also simultaneously suppresses controllable spin transport. Such dilemma has been a major roadblock for realization of practical spintronic devices such as spin field effect transistors. In this project, by using semiconducting ferroelectric materials of selected symmetry with strong spin-orbit coupling, the PI expects to achieve symmetry-protected long-range coherent spin transport via persistent spin helix and switchable spin texture upon changing the ferroelectric polarization. To pursue these goals, the PI will grow high-quality single crystalline ferroelectric semiconductors carrying strong spin-orbit coupling, and fabricate ferroelectric spin valves and field effect transistors. The PI will investigate the spin-polarized band structure and persistent spin helix in the model materials. The PI will reveal the spin lifetime and spin diffusion length in ferroelectric spin valves and field effect transistors. The PI will also study the dynamics of ferroelectric domain structure and effect of ferroelectric domain orientation on persistent spin helix, spin dynamics, spin operation and diffusion. This proposed work will advance the fundamental knowledge needed in resolving the intrinsic dilemma issue between the precise manipulation and effective preservation of spin in spintronic systems with strong spin-orbit interaction.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.