CAREER: Controlling unconventional interactions between 2D excitons and novel quantum excitations

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Nontechnical Abstract: When a semiconductor absorbs light, some electrons can be freed, and the vacancies left behind behave like particles with positive charge (called “holes”). In atomically thin semiconductors, the electrons and holes can attract each other to form robust bound states (called excitons). As the excitons govern properties of these materials, it is crucial to explore new excitonic physics to develop the next-generation semiconductor technology. This research explores novel phenomena induced by strong interactions between excitons and other particles. The research team controls the interactions by tuning the exciton properties. The research can reveal new types of complex excitonic states and develop new techniques to transmit information with the excitonic states. A comprehensive education and outreach plan is incorporated to introduce high-school and undergraduate students to current scientific research and help underrepresented students to pursue higher education in science and technology.Technical Abstract: Atomically thin two-dimensional semiconductors are a new class of materials for fundamental condensed matter research and novel applications. The optical properties of these materials are dominated by tightly bound excitons with remarkable properties. This research explores new quantum phenomena by controlling the interactions between two-dimensional excitons and three types of quantum states, including chiral phonons, Fermi-sea electron-hole excitations, and Landau levels. Unlike some other research that studies excitons in relatively weak and simple interaction conditions, this research focuses on excitons under strong and complex interaction conditions, which are specifically realized by: (1) coupling to chiral phonons, (2) using large excited-state excitons, and (3) shaping excitons into Landau orbits under high magnetic field. Under these interaction conditions, the research can bring forth a panoply of exotic quantum phenomena, such as trion and phonon Hall effect, phonon-photon entanglement, exciton-polaron formation, and fractional quantum Hall excitonic states. The study of these phenomena can greatly uplift our understanding of complex excitonic dynamics under strong, chiral, and quantum-entangled interaction conditions. The research can also lead to new designs in novel excitonic and phononic devices for excitonic transport, phonon transport, energy harvesting, and valleytronic information technology.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.