Exploring 2D Van der Waals Heterostructures with Layered Magnets for Valley-Based Electronics and Optoelectronics

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Nontechnical description: The control of magnetism, which lies at the heart of modern information technology, is typically achieved by using another magnet. This approach significantly limits the size of devices for information processing. There is a pressing need to develop non-magnetic approaches to control magnetism for better information technology. This project aims to develop a new class of composite magnetic materials of nanometers in thickness, whose magnetic properties can be effectively switched through an electric field. Such an operation is much more energy-efficient since it avoids heating of the electronic device. The research employs atomically thin crystals, including both magnetic and non-magnetic semiconductors, and stacks them vertically by design. These composite materials are studied to understand how their structural characteristics may lead to improved magnetic properties, and to develop device concepts for applications in electronics and optoelectronics. This project supports the research and development of one graduate student. In addition to training in research, the student develops other skills for teaching in the STEM (Science, Technology, Engineering, and Mathematics) disciplines at the university level by working with the Cornell University Center for the Integration of Research, Teaching, and Learning. The Principal Investigator is incorporating state-of-the-art research concepts such as modern optical microscopy into an undergraduate lab course, while also overseeing outreach activities targeting younger students and their teachers.Technical description: A large family of two-dimensional materials that possess interesting properties individually has been discovered in recent years. Stacking different two-dimensional materials to form van der Waals heterostructures has opened up unprecedented opportunities for exploring new physical phenomena and device concepts. This project aims to develop a new class of ferromagnetic semiconductors based on magnetic proximity coupling between single-layer non-magnetic semiconductors, such as transition metal dichalcogenides that exhibit interesting valley-dependent properties, and layered magnets, such as transition metal trihalides. The research combines materials fabrication and optical, structural and transport characterization to achieve three objectives: (1) Demonstrate and understand electrical switching of magnetic order in layered magnets; (2) Develop heterostructures of non-magnetic semiconductors and layered magnets with strong magnetic proximity coupling and demonstrate electrical switching of the valley properties of the heterostructures; and (3) Explore the transport and optical properties of the heterostructures for electrically switchable valley-dependent electronic and optoelectronic devices. The results of this project have the potential to impact a range of diverse fields including spintronics and valleytronics, as well as improve understanding of interfacial phenomena in low-dimensional systems. The project supports the scientific training and professional development of one graduate student, as well as education and outreach activities at all levels, while focusing on introduction of state-of-the-art research concepts.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.