The materials engineering and design of metals have enjoyed great freedom from the abundant choices of metal elements in the periodic table. Yet this immense chemical space is difficult to access for atomically-thin two-dimensional metals, since 2D metals would be fragile against oxidation. The recent stabilization of 2D metals at the graphene/SiC interface establishes a means to synthesize air-stable 2D metals at scale. Employing first-principles high-throughput computation, we survey the structures and stabilities of all metals in the periodic table that would intercalate a graphene/SiC interface. Trends in the stabilities and structures of these systems follow general rules in metal-metal and metal-silicon bonding. The lowered dimensionality allows some 2D metals to be semiconducting when two conditions are met: appropriate electron filling and substrate-induced symmetry breaking. From this gapping stabilization, we derive alloying rules unique to 2D metals. Finally, we discuss superconductivity and record-breaking nonlinear optical response in 2D gallium and indium, as established through joint theoretical and experimental work.
Dr. Yuanxi Wang is an assistant professor at UNT physics department. After obtaining Ph.D. in physics at the Penn State University in 2016, he was a postdoctoral researcher and then an assistant research professor at the Penn State Materials Research Institute, prior to joining UNT physics in 2021. He has strong research interests in developing computational materials theory, as applied to 2D materials like graphene and layered compounds. His most recent interests include defect-based qubits in 2D semiconductors, exciton physics in 2D materials, and modeling large-area growth of highly crystalline 2D crystals. His work also involves tight collaborations with experimentalists across multiple disciplines, with focus on the optical, mechanical, transport, and catalytic properties of 2D materials.