CAREER: Topological Phenomena in 4d and 5d Complex Oxide Interfaces and Superlattices Grown by Hybrid Molecular Beam Epitaxy

NON-TECHNICAL DESCRIPTION: Thin films of metal oxides such as ferrous oxide and titania have long been studied for their various unique physical properties, such as magnetism and superconductivity. It is only in the past few years, however, that research in oxides comprised of metallic elements lower in the periodic table has gained prominence. Oxides composed of these metals exhibit unusual properties when they conduct electricity making them strong candidates for use in quantum computation technologies.

This project focuses on the synthesis of oxide thin films comprised of elements in the fourth and fifth rows of the periodic table. Researchers are studying the unusual behavior derived from materials comprised of two different elements made with atomically sharp interfaces using a technique called molecular beam epitaxy. By alternating layers of each material in a sandwich structure to produce repeating interfaces, the research focuses on making a material that exhibits the properties of the interface many times over.

Through two outreach programs, exposure to science in rural and underserved areas of Alabama is broadened to groups that are not introduced to science in their daily lives. The investigator teaches annual seminars in Alabama prisons through the Alabama Prison Arts and Education Project about the applications of physics and materials science to new technologies, offering non-traditional students scientific enrichment and education during their rehabilitation that is not otherwise available.

The researchers also lead the annual Gameday Physics outreach event to perform science demonstrations and introduce physics research to a broad and diverse audience at highly-attended football games on the Auburn University campus.

TECHNICAL DETAILS: Complex oxides comprised of 4d and 5d transition metals exhibit significantly higher spin-orbit coupling than those comprised of 3d elements. These materials have been predicted to exhibit high temperature superconductivity and other emergent topological phenomena when formed in epitaxial thin film heterostructures and superlattices.

These properties make 4d and 5d materials promising for use as materials to enable topological quantum computation. In this project, systematic studies of synthesis of several candidate 4d and 5d complex oxides via hybrid molecular beam epitaxy are performed. Using this novel approach, a metal-organic precursor replaces the traditional elemental source for the transition metal, enabling easier synthesis and producing higher quality materials.

Exploration of emergent interfacial phenomena includes high-temperature superconductivity, ferroelectricity, and topological electronic states. By synthesizing superlattice films comprised of repeating interfaces, the research focuses on the development of materials that exhibit interfacial phenomena in a bulk film. This project provides educational experiences for undergraduate students to learn about materials characterization through machine learning analysis of diffraction and spectroscopy data.

Computational codes to analyze such data are shared for the research community to advance real-time analysis of film synthesis. Graduate student researchers gain experience in materials synthesis and characterization in the lab and at user facilities around the world. Such experiences help prepare students for careers in materials research in the integrated circuit and electronic device industry.

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.