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

非技术描述：厚度只有一个或几个原子层的材料表现出与大块材料的电子性质相比发生了深刻变化的电子性质。这些行为可以被用来设计具有新功能的新型光电子器件。这项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性和电学性质。该团队设想了一种材料，只要拨动开关，就可以变成导电或绝缘的，磁性的或非磁性的。这种材料将对高密度存储设备和超灵敏磁或光传感器等新技术的发展至关重要。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，这两个团队成员都积极从代表性不足的群体中招聘和指导本科生和研究生，同时也向高中教师和学生伸出援手。该团队与佛罗里达州立大学国家高磁场实验室合作，为佛罗里达州北部周边县的学校开发动手教学材料。技术描述：根据最近的一项理论提议，该研究项目的最终目标是实现由于单层和少层金属单醇化合物中的半金属性质而实现栅极可调铁磁性。这些化合物，即(In，Ga)(S，Se，Te)，已被证明具有高的室温载流子迁移率，与厚度相关的带隙和高的光响应性。虽然单硫化物是非磁性的，但最近的第一性原理计算预测了它们的单层中的自旋分裂价带，磁矩和自旋极化能量都强烈地依赖于密度。因此，随着空穴密度的调节，有望实现正常的金属-铁磁-正常金属转变，当原子薄的单金属化合物空穴掺杂到~1013/cm2时，会出现铁磁性和半金属性质。本研究项目致力于通过克服一些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栅极技术。该研究计划的成功实施有望导致新的半金属系统，该系统可以与异质结构中的其他层状化合物结合，产生新的功能。除了培训研究生，两位主要研究人员都继续他们既定的努力，指导本科生和高中生，同时也从代表不足的群体中招募和指导学生。这一奖项反映了NSF的法定使命，并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。

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.