Collaborative Research: Harvesting electronic flat bands and strong spin-orbit coupling for novel functionalities in metal monochalcogenides

非技术描述由单个原子层或几层原子层制成的材料具有与块状材料截然不同的电子特性。例如，二维材料可以结合高机械强度和光学透明度以及高效的电荷传输。这些特性可以用来创造具有新功能的新型设备。人们可以制造出一种材料，它可以导电或绝缘，也可以磁性或非磁性，只要按一下开关。这种材料可以用于开发超灵敏的光学或磁传感器。该研究项目将重点研究一类超薄材料——金属单硫族化合物，如硒化镓或硫化镓。研究人员将对这些材料进行研究，并在剥离、封装和扭转时赋予它们特定的电、磁和光学特性。这项研究将与下一代物理学家、材料科学家和工程师的指导和培训相结合。这两个团队成员都积极地从代表性不足的群体中招募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的国家高磁场实验室合作，为北佛罗里达周边县的学校开发动手教学材料。该合作项目的目标是利用III-VI金属单硫族化合物（MMCs）家族固有的电子平带和强自旋轨道耦合（SOC），在大SOC的限制下实现门可调谐铁磁性和半金属性，分数量子霍尔（QH）态。这项工作将使新型自旋电子、谷电子和光电子器件成为可能。研究人员将：i)探索、调整和理解大型SOC体系中分数量子霍尔态的性质，这对拓扑量子计算具有重要意义；ii)由于半金属性及其与其他可能的相关态（如可能的超导性和相关相）的相互作用，在空穴掺杂的少层mmc中实现门可调铁磁性；iii)在过渡金属二硫族化合物上基于金属单硫族化合物的异质结构中产生自旋和谷极化电流，以及iv)在具有摩尔超晶格的MMC异质结构中实现栅极可调激子，用于光电子学，具有前所未有的可调性。该项目将直接资助每个参与机构的一名研究生。这些学生将在两所院校和其他国家机构之间流动。此外，两位主要研究人员将继续他们在指导本科生和高中生方面的既定努力，同时也会从代表性不足的群体中招募和指导学生。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。

NON-TECHNICAL DESCRIPTIONMaterials made from a single atomic layer or a few layers have electronic properties that profoundly differ from those of bulk materials. For example, two-dimensional materials can combine high mechanical strength and optical transparency with efficient charge transport. These properties could be exploited to create new classes of devices with novel functionalities. One could make a material that could become electrically conducting or insulating, but also magnetic or non-magnetic, at the flip of a switch. Such a material could enable development of ultra-sensitive optical or magnetic sensors. This research project will focus on one class of ultrathin materials—metal monochalcogenides such as gallium selenide or gallium sulfide. Researchers will investigate these materials and seek to endow them with specific electrical, magnetic, and optical properties upon exfoliation, encapsulation and twisting. This research will be integrated with the mentoring and training of the next generation of physicists, materials scientists, and engineers. Both team members actively recruit and mentor undergraduate and graduate students from underrepresented 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 the surrounding North Florida counties.TECHNICAL DESCRIPTIONThe goal of this collaborative project is to harness the electronic flat bands and strong spin-orbit coupling (SOC) inherent to the family of the III-VI metal monochalcogenides (MMCs), to achieve gate-tunable ferromagnetism and half-metallicity, fractional quantum Hall (QH) states in the limit of large SOC. The work will enable novel spintronic, valleytronic and optoelectronic devices. Investigators will: i) explore, tune, and understand the nature of the fractional quantum Hall states in the regime of large SOC, which has implications for topological quantum computation; ii) achieve gate-tunable ferromagnetism due to half-metallicity and their interplay with other possible correlated states (such as possible superconductivity and correlated phases ) in hole-doped few-layer MMCs; iii) create spin- and valley-polarized currents in heterostructures based on metal monochalcogenides on transition metal dichalcogenides, and iv) achieve gate-tunable excitonics in MMCheterostructures with moiré superlattices, for optoelectronics with an unprecedented level of tunability. This project will directly support one graduate student at each participating institutions. The students will circulate among both institutions and other national facilities. In addition, both principal investigators will 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.