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

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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.