Collaborative Proposal: Quest for an Electric field-Induced Half-Metallic State in Metal Monochalcogenides

合作提案：寻找金属单硫族化物中电场诱导的半金属态

• 批准号: 1807928
• 负责人: Chun Ning Lau
• 金额: $ 25万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1807928&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Quest; Electric; field

Non-technical Description: Materials that are only a single or few atomic layers in thickness exhibit electronic properties that are profoundly altered with respect to those of bulk materials. These behaviors can be exploited for engineering new classes of optoelectronic devices with novel functionalities. The goal of this research project is to investigate a class of such extremely thin materials that are only one or few atomic layers thick, and seek to endow them with specific magnetic and electronic properties. The team envisions a material that, at the flip of a switch, can become electrically conducting or insulating, magnetic or non-magnetic. Such a material would be vital for the development of new technologies such as high-density memory storage devices and ultra-sensitive magnetic or optical sensors. These research efforts are integrated with plans to mentor and train the next generation of physicists and material scientists. In addition, both team members are active in recruiting and mentoring undergraduate and graduate students from under-represented groups, while also reaching out to high school teachers and students. The team collaborates with the National High Magnetic Field Laboratory at Florida State University to develop hands-on instructional materials for schools in surrounding North Florida counties.Technical Description: The ultimate goal of this research project is the achievement of gate-tunable ferromagnetism due to half-metallicity in monolayer and few-layer metal monochalcogenides, based on a recent theoretical proposal. These compounds, i.e. (In,Ga)(S, Se, Te), have been shown to exhibit high-room-temperature carrier mobility, thickness-dependent band gaps and high photoresponsivities. Although monochalcogenides are nonmagnetic, a recent first principles calculation predicts spin-split valence bands in their monolayers, with both the magnetic moment and the spin polarization energy depending strongly on density. Thus, a normal metal-ferromagnet-normal metal transition is expected as the hole density is tuned, with ferromagnetism and half-metallicity emerging when atomically thin monochalcogenides are hole-doped to ~10^13/cm^2. This research project strives to achieve this ambitious goal by overcoming a number of critical challenges, including synthesis of high quality material, device fabrication and optimization, and efficient gating techniques. Successful implementation of the research plan is expected to lead to new half-metallic systems that can be combined with other layered compounds in heterostructures to produce novel functionalities. In addition to training graduate students, both principal investigators continue their established efforts at mentoring undergraduate and high school students, while also recruiting and mentoring students from underrepresented groups.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.

非技术描述：厚度仅为单个或几个原子层的材料表现出的电子特性与块状材料相比发生了深刻的改变。这些行为可用于设计具有新颖功能的新型光电器件。该研究项目的目标是研究一类只有一个或几个原子层厚的极薄材料，并寻求赋予它们特定的磁和电子特性。该团队设想了一种材料，只要按下开关，就可以导电或绝缘、磁性或非磁性。这种材料对于高密度内存存储设备和超灵敏磁性或光学传感器等新技术的开发至关重要。这些研究工作与指导和培训下一代物理学家和材料科学家的计划相结合。此外，两位团队成员都积极招募和指导来自代表性不足群体的本科生和研究生，同时也接触高中教师和学生。该团队与佛罗里达州立大学国家高磁场实验室合作，为北佛罗里达州周边县的学校开发实践教学材料。技术描述：该研究项目的最终目标是实现门可调谐铁磁性，因为一半-基于最近的理论建议，单层和少层金属单硫属化物的金属性。这些化合物，即 (In,Ga)(S, Se, Te)，已被证明具有高室温载流子迁移率、厚度相关的带隙和高光响应性。尽管单硫属化物是非磁性的，但最近的第一原理计算预测了其单层中的自旋分裂价带，其中磁矩和自旋极化能都强烈依赖于密度。因此，随着空穴密度的调整，预计会出现正常金属-铁磁体-正常金属转变，当原子薄的单硫属化物空穴掺杂至~10^13/cm^2时，会出现铁磁性和半金属性。该研究项目致力于通过克服许多关键挑战来实现这一雄心勃勃的目标，包括高质量材料的合成、器件制造和优化以及高效的门控技术。该研究计划的成功实施预计将产生新的半金属系统，该系统可以与异质结构中的其他层状化合物结合以产生新的功能。除了培养研究生之外，两位主要研究者还继续他们在指导本科生和高中生方面的既定努力，同时还招募和指导来自代表性不足群体的学生。该奖项反映了 NSF 的法定使命，并通过使用基金会的评估进行评估，认为值得支持。智力价值和更广泛的影响审查标准。