DMREF Collaborative Research: Establishing the platform of quasi-one-dimensional topological insulators with emergent functionalities

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Non-technical Description: Applying the concept of topology to solid state systems has revolutionized our understanding of quantum phenomena and materials, and inspired the design of new functionalities in electronic, atomic, photonic, mechanical, and acoustic systems. For instance, topological insulators (TIs) are a class of materials that are electrically insulating in the bulk, but host conductive surface states. Protected by symmetry and topology, these surface states are immune to impurities and thus enable making near-perfect devices from imperfect interfaces, which are important for both conventional and quantum information technology. However, there exist a number of critical challenges in current TI materials that must be addressed before realizing their full potential. This project aims at overcoming these challenges by focusing on a new class of materials, quasi-one-dimensional (quasi-1D) TIs with emergent functionalities. An iterative loop of theoretical modeling and prediction, material synthesis, and characterization will be established to discover different families of quasi-1D TIs and explore their unique properties for topological phenomena and functionalities. The project's success will shed light on the realization of topological quantum computing and low-power spintronics for next-generation information technology and sustainable energy solutions. Major educational activities will be integrated into the research activities by performing public outreach, training graduate and undergraduate students, increasing participation of under-represented groups, providing a new face to physics and materials science with two women in leadership positions on this team, and offering open access to research and education outputs to the technical community and general public.Technical Description: To date, most of the identified TIs are either strongly bonded bulk materials or layered van der Waals materials. Despite their richness, fundamental obstacles and limitations exist in exhibiting the decisive properties and realizing the full promise of TIs, such as the restriction of surface Dirac cones to a specific cleavage plane, weak electronic interactions and limited tunability. Remarkably, a quasi-1D structure promises to overcome these challenges. The goals of this project include design and optimization of quasi-1D TI candidates, synthesis and characterization, tuning topological phase transitions by strain and temperature, and seeking 2D TIs in atomically thin layers of quasi-1D materials. Through complementary expertise and concerted efforts on theory and computation, material synthesis, spin- and angle-resolved photoemission spectroscopy, nanofabrication, quantum transport, and neutron and x-ray scattering, the project is expected to lead to the discovery of novel TIs, phases and phenomena, controlling topological transitions, and enabling superior functionalities and fostering quantum technologies.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.