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

提出的研究将通过实现新设备技术的创新来影响社会。将继续实施一项培训下一代研究人员和增加代表不足群体的参与的计划。通过这一研究计划，将建立一个多年的指导计划，为少数族裔服务机构的主要调查实验室的本科生提供研究经验。将制定面向公众的外联计划，目标是宾夕法尼亚州西南部地区代表人数较少的少数族裔的K-12学生。同时，将开发一门通过动手实验教授量子物理基本概念的课程。本课程将提供为美国新兴产业培养下一代量子劳动力的教育。新型量子材料中的新兴现象是实现计算、数据存储和高频电子设备转型的关键。对于磁存储器件，拟议的研究将实现备受追捧的两端自旋轨道扭矩磁存储器件，以实现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，需要占用空间小的硬件节点来实现存储元件的密集网络。然而，到目前为止，该领域中考虑的自旋轨道扭矩驱动磁存储器件有三个端子，其中磁隧道结集成在自旋源材料的顶部，以通过隧道磁阻效应来读取状态。自旋轨道扭矩驱动的磁存储器件被认为是高能效的，因为在磁化操作中，由自旋霍尔效应现象产生的自旋电流比用于基于磁隧道结的器件中使用的自旋极化电流更有效。然而，一个基于自转轨道力矩的两端装置已经严重缺失。这项研究计划将展示一种用于磁存储应用的基于自旋轨道力矩的双端设备的原型，在该设备中，由于Weyl半金属中的面外自旋电流，使用一种新的磁阻来读取磁状态。此外，二维磁体中磁相互作用的电子调谐可以实现灵活的微波设备，如可调带通滤波器。基于磁性材料中自旋波激发的微波滤波器具有实现紧凑型、平面型和频率捷变等功能的潜力。然而，对于微波器件来说，实现自旋波激励的电可转换性是非常必要的，但它仍然具有挑战性。自旋波激励决定了磁基带通滤波器的通过和抑制频率。这项研究计划将探索和演示用于制作电场可调带通滤波器件原型的二维磁体中磁各向异性的栅极电压调谐。将开展一项研究计划，旨在利用Weyl半金属和二维磁体中的紧急自旋现象，为下一代存储器和高频器件提供变革性器件功能的实验演示。该研究计划的具体科学目标有两个：(1)展示基于两端自旋轨道扭矩的磁记忆单元，其中信息存储在具有垂直磁各向异性的铁磁体的磁态中，磁状态由自旋轨道扭矩现象写入，并通过Weyl半金属中倾斜的自旋电流产生的新型磁阻来读取状态；(2)将展示基于二维磁体的电场可调带通滤波器。研究了利用磁各向异性来调谐磁体磁共振的电场可调性，这是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，从而建立起微波器件的通带和抑制带。对于建议的带通滤波器，将对插入损耗、带通滤波器中心频率、工作带宽和其他设备参数进行表征。该奖项反映了NSF的法定使命，并已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。

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.