Investigating many-body states of interlayer excitons in 2D atomic double layers

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Nontechnical: Bose-Einstein Condensates are a state of matter predicted by Bose and Einstein nearly a century ago and has been realized in dilute gases of atoms at temperatures close to absolute zero. This discovery has led to tremendous advances in science, precision measurements and quantum information. However, one big hurdle for further technological advances is the extremely low temperature that is required to create these condensates. In this project, the research team develops a new type of Bose-Einstein Condensates formed at high temperatures (100 K). The artificial atoms are formed in atomically thin membranes of materials that are stacked layer-by-layer. This could result in development of high temperature superconductors and optoelectronic, photonic and quantum devices with unprecedented properties. The project trains graduate and undergraduate students, preparing them as workforce in emerging quantum technologies. The team also develops outreach materials for use in inspiring and broadening participation among young students.Technical: Bose-Einstein condensation (BEC) of a dilute gas of atoms occurs at temperatures close to absolute zero. With much smaller mass, excitons (bound electron-hole pairs) are expected to condense at considerably higher temperatures. The emergence of two-dimensional layered semiconductors with very strong exciton binding (about half an electron volt) and flexibility in forming van der Waals heterostructures has opened a new exciting opportunity to explore high-temperature exciton condensate and other emergent quantum many-body ground states. This research project builds on the principal investigator’s prior works and expertise in van der Waals heterostructures and aims to develop new solid-state structures for exciton condensation and exciton condensate-based applications in optoelectronics and photonics. By using optimized design of the double layer structure and an array of experimental probes based on electrical transport and optical measurements, the team aims to achieve three objectives. (i) Search for direct evidence of exciton condensation in transition metal dichalcogenide (TMD) double layers such as long-range spatial coherence; (ii) Map the exciton condensation temperature - density phase diagram in the BEC regime and near the BEC to Bardeen-Cooper-Schrieffer (BCS) crossover; (iii) Search for equilibrium exciton condensates in double layer systems consisting of small gap semiconductors.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.