Collaborative Research: Spin Physics `by design' in quantum dot molecules

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Non-TechnicalModern electronic devices (e.g. computer hard drives) use "spin" to store information. Other optoelectronic devices (e.g. lasers) use light to transmit information. This project investigates new materials that could integrate these two functions in a single system. We will explore the properties of coupled pairs of semiconductor quantum dots that behave like molecules with unique and tunable properties. The results will provide the scientific foundation for building faster and more powerful computing, information transmission and information storage devices. The project will train graduate students in the conduct of research. It will also help to inspire and educate younger students by bringing hands-on scientific experiments into K-12 classrooms. TechnicalCoupled pairs of semiconductor quantum dots are called quantum dot molecules because coherent tunneling between the individual quantum dots leads to the formation of molecular states with unique and tunable properties. This project will develop the scientific foundation for predictive design of tailored properties for individual charges confined within quantum dot molecules. To accomplish this objective, the research team is investigating specific changes in the structure, composition and electric field environment of the quantum dot molecule that they hypothesize will lead to new optoelectronic and spin properties. The team will grow designed quantum dot molecules using molecular beam epitaxy and fabricate device structures that allow application of two-dimensional electric field profiles that break the molecular symmetry. The resulting optoelectronic and spin properties will be characterized with optical spectroscopy at low temperatures and in high magnetic fields. The team will develop the computational tools necessary to accurately predict the properties of new quantum dot complexes that incorporate nontraditional materials such as GaBiAs and rare-earth nanoinclusions. Close interaction between theory and experiment will allow refinement and validation of the computational models, setting the stage for predictive engineering of solid state nanostructures with tailored properties.