Design of Complex Oxide Interfaces by Oxide Molecular Beam Epitaxy

Complex oxides provide a versatile playground for many phenomena and possible applications, for instance, high-temperature superconductivity, magnetism, ferroelectricity, metal-to-insulator transition, colossal magnetoresistance, and piezoelectricity. The origin of these phenomena is the competition between different degrees of freedom such as charge, orbital, and spin, which are interrelated with the crystal structure, the oxygen stoichiometry, and the doping dependence. Recent developments not only in the epitaxial growth technologies, such as reactive molecular beam epitaxy, but also in the characterization techniques, as aberration-corrected scanning transmission electron microscopy with spectroscopic tools, allow synthesizing and identifying epitaxial systems at the atomic scale. Combination of different oxide layers opens access to interface physics and leads to engineering interface properties, where the degrees of freedom can be artificially modified. In this review, we present different homo- and hetero-epitaxial interfaces with extraordinary structural quality and different functionalities, including high-temperature superconductivity, thermoelectricity, and magnetism.