Twistronic and spatial modulation of spin orbit coupling for spintronic and topological devices

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Nontechnical descriptionIn addition to charge, electrons also possess an intrinsic spin that produces a magnetic moment like a tiny bar magnet. Spintronics, i.e. manipulation and control of electron spin for technological applications, has led to technological breakthroughs such as the magnetic memory that is widely used in hard drives today. Achieving yet greater ability to harness spin-related phenomena in the nanoscale promises the development of novel devices for data storage and information processing. This research project aims at manipulating spin via controlling so-called spin-orbit coupling (SOC) of charges, which couples the spatial motion of the electron to its spin. This is achieved by taking advantage of atomically thin two-dimensional materials that are stacked together, so as to create heterostructure materials with regions of different SOC strengths. For example, while graphene has very low SOC, when stacked onto transition metal dichalcogenide (TMD) materials its SOC becomes significant. The research team creates devices with tunable spatial distribution, magnitude and direction of SOC, and realizes topological superconductivity that could potentially form a basis for quantum information processing. This research is integrated with a comprehensive course of education and training of undergraduate and graduate students for the next generation of the quantum workforce.Technical descriptionWhile SOC enables new ways to control spin in nanostructures and produce new topological electronic ground states, it can also reduce spin lifetimes. As two-dimensional materials allow tunable SOC, they provide a promising platform to harness SOC for spin manipulation while enabling long spin lifetime. This research project builds on the team’s prior works and expertise in fabricating high mobility graphene/TMD heterostructures and aims to develop new classes of spintronic and topological devices based on twistronic and spatial engineering of SOC. Goals include (1). Using graphene/TMD interlayer twist angle and Fermi level tuning to control the magnitude and type of SOC (Rashba vs. Ising); (2). Spatial SOC manipulation to achieve spin-valley valves and generation of pure spin currents; and (3). realizing topological superconductivity by coupling graphene/TMD heterostructures to superconductors, which is tunable in situ for example by varying the Fermi energy in graphene and engineerable by varying the twist angle. Successful research project implementation will lead to the manipulation of spins without magnetic materials or magnetic fields and a major step towards developing building blocks for fault-tolerant quantum computation. In addition to training graduate students, the research team members will continue their established efforts at mentoring undergraduate and high school students in addition to recruiting and mentoring 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.