CAREER: Design, control, and understanding of lateral textures in strongly correlated heterostructures

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Non-technical abstract Among the biggest triumphs of 20th-century solid-state physics was the quantum-mechanical description of metals, semiconductors, and insulators. This successful model for simple materials like Silicon propelled the technological revolution after achieving control of its properties at the nanometer scale to make small devices. However, there are fundamental limits on reducing their size, prompting the exploration of new materials to render novel functionalities. Thus, major research efforts worldwide explore a new class of materials governed by more complex quantum mechanical principles, known as “quantum materials”, to advance the technological revolution. Still, control of their properties at small sizes has proven to be challenging. This project has the goal of gaining control of the electronic behavior of quantum materials at the nanometer scale. The research team uses newly discovered techniques to modify a material’s chemistry and concentration of electrons at the atomic level, which will give us control of the electronic properties with exquisite lateral spatial resolution down to the nanometer range. With this knowledge, novel device concepts with far-reaching implications will be developed. Students are trained on materials physics, device concepts, and cutting-edge experimental techniques and analysis within a framework that supports minority students. Furthermore, to broaden the impact of the research a podcast is produced that showcases the importance and successes of research on solid state physics.Technical abstract This project stems from the motivation to gain control of the fascinating electronic properties of strongly correlated transition metal oxides at the nanometer scale. These “quantum materials” are a topic of high interest because of their complex and tunable quantum phases. Soon after, it was realized that growing them epitaxially in thin films and superlattices could provide ways of tuning the properties. However, lateral control of the quantum properties has been deemed difficult. This project has two ways to laterally modify these properties with a spatial resolution at nano- to mesoscopic length scales. First, the research team uses a beam of He ions focused down to nm, which can change a material’s oxidation state and thus gain exquisite control of the ground state properties. Secondly, since layering a quantum material next to an optoelectronic semiconductor can yield a dramatic sensitivity of the former to light stimulus, the team patterns the growth of the optoelectronic layer such as to create light-sensitive areas on the heterostructure, where the quantum phases are distinct from the areas without an optoelectronic layer on top. Students involved in the research acquire knowledge of modern materials science and state-of-the-art x-ray spectroscopic tools at synchrotron facilities. The project also builds a framework to support students of minority backgrounds and produces an audio podcast that describes the successes of last-century solid state physics highlighting its real-world implications.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.