CAREER: Next-generation Logic, Memory, and Agile Microwave Devices Enabled by Spin Phenomena in Emergent Quantum Materials

所提出的研究将通过创新来实现新的设备技术，从而影响社会。将推行培训下一代研究人员和增加代表性不足群体参与的项目。通过该研究项目，将建立一个多年的指导项目，为来自少数民族服务机构的首席研究员实验室的本科生提供研究经验。针对公众的外展项目将被开发出来，并将针对宾夕法尼亚西南部地区少数族裔的K-12学生。同时，还将开设一门课程，通过动手实验来教授量子物理的基本概念。本课程将为美国新兴产业培养下一代量子劳动力提供教育。新型量子材料中的涌现现象是实现计算、数据存储和高频电子器件变革性设备的关键。对于磁存储器件，本研究将实现一种备受追捧的双端自旋轨道转矩磁存储器件，用于节能和超紧凑的数据存储。为了构建具有行业竞争力的磁存储设备，需要一个占用空间小的硬件节点来实现密集的存储元素网络。然而，目前在该领域考虑的自旋轨道转矩驱动磁存储器件有三个终端，其中一个磁隧道结集成在自旋源材料上，通过隧道磁电阻效应读取状态。由于自旋霍尔效应产生的自旋电流比基于磁隧道结的自旋极化电流更有效地控制磁化，因此自旋轨道转矩驱动的磁存储器件被认为是高能效的。然而，一种基于自旋轨道扭矩的双端装置一直严重缺乏。本研究计划将展示一个用于磁存储应用的基于自旋轨道转矩的原型双端器件，其中利用Weyl半金属中的面外自旋电流使用一种新型磁电阻读取磁态。此外，二维磁体中磁相互作用的电调谐可以实现灵活的微波器件，例如可调谐带通滤波器。基于磁性材料中自旋波激励的微波滤波器具有实现紧凑、平面和频率敏捷等功能的潜力。然而，实现自旋波激励的电可转性，这决定了基于磁铁的带通滤波器的通过和拒绝频率，是微波器件非常需要的，但它仍然具有挑战性。本研究计划将探索并演示二维磁体中磁各向异性的栅极电压调谐，用于原型电场可调谐带通滤波器器件。一项研究计划旨在利用Weyl半金属和二维磁体中的新兴自旋现象，对下一代存储器和高频器件的变革性设备功能进行实验演示。本课题的具体科研目标是：(1)构建基于双端自旋轨道转矩的磁记忆单元单元，将信息存储在具有垂直磁各向异性的铁磁体的磁态中，通过自旋轨道转矩现象写入磁态，并通过Weyl半金属中倾斜自旋电流产生的新型磁电阻读取磁态；(2)展示了一种基于二维磁体的电场可调谐带通滤波器。利用磁场各向异性的电场可调性来调节磁体的磁共振，这是频率捷变带通滤波器的关键特性，因为电场的作用会改变谐振频率的位置，从而建立微波器件的通阻带。对于提议的带通滤波器，插入损耗、通滤波器中心频率、工作带宽和其他器件参数将被表征。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。

The proposed research will impact society through the innovation to realize new device technologies. A program to train next-generation researchers and increase underrepresented groups’ participation will be pursued. A multi-year mentoring program, which will provide research experience for undergraduate students in the principal investigator’s lab from minority serving institutions will be established through this research program. Outreach programs for the public will be developed and will be targeted towards K-12 students belonging to underrepresented minorities in southwestern Pennsylvania area. In parallel, a course to teach fundamental concepts of quantum physics through hands-on experiments will be developed. This course will provide education to produce the next-generation quantum workforce for emergent industries in the United States.Emergent phenomena in novel quantum materials are key to enable transformative devices for computing, data storage, and high-frequency electronics. For magnetic memory devices, the proposed research will enable a much sought after two-terminal spin-orbit torque magnetic memory device for energy efficient and ultra-compact data storage. To build an industry competitive magnetic memory device, a small footprint hardware node is desired to implement a dense network of storage elements. However, spin-orbit torque driven magnetic memory devices considered so far in the field have three terminals, wherein a magnetic tunnel junction is integrated on top of spin-source material to read the state through tunnel-magnetoresistance effect. The spin-orbit torque driven magnetic memory devices are envisioned to be highly energy-efficient because spin current induced by spin Hall effect phenomena is more efficient at magnetization manipulation than spin-polarized current used in magnetic tunnel junction-based devices. However, a spin-orbit torque based two-terminal device has been critically missing. This research program will demonstrate a prototype spin-orbit torque based two-terminal device for magnetic memory applications in which the magnetic state is read using a new kind of magnetoresistance owing to out-of-plane spin current in Weyl semimetals. Additionally, the electrical tuning of magnetic interactions in two-dimensional magnets can enable agile microwave devices, such as tunable band-pass filters. Microwave filters based on spin-wave excitations in magnetic materials have the potential to realize functionalities such as compactness, planar, and frequency-agility. However, achieving an electrical turnability of spin-wave excitations, which decides the pass and rejection frequency of a magnet based band-pass filter, is highly desired for microwave devices but it remains challenging. This research program will explore and demonstrate gate voltage tuning of magnetic anisotropy in two-dimensional magnets for prototyping electric-field tunable band-pass filter devices. A research program aimed at experimental demonstration of transformative device functionalities for next-generation memory and high-frequency devices using emergent spin-phenomena in Weyl semimetals and two-dimensional magnets will be pursued. The specific scientific goals of this research program are twofold: (1) A two-terminal spin-orbit torque based magnetic memory unit cell will be demonstrated, wherein the information is stored in the magnetic state of ferromagnet with perpendicular magnetic anisotropy, the magnetic state is written by the spin-orbit torque phenomena, and the state is read through a new type of magnetoresistance owing to tilted spin current in Weyl semimetals; (2) An electric-field tunable band-pass filters based on two-dimensional magnets will be demonstrated. The electric field tunability of magnetic anisotropy to tune the magnetic resonance of a magnet will be explored, which is the key characteristic of a frequency agile band-pass filter because the application of electrical field will shift the location of resonance frequency to set up the pass and rejection band of the proposed microwave device. For proposed band-pass filters, insertion loss, pass-filter center frequency, operational bandwidth, and other device parameters will be characterized.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.