The goal of this project is to create, characterize and control novel quantum states of condensed matter at the interfaces of complex oxide materials using atomic layer-by-layer synthesis and recently pioneered methodologies for advanced characterization with synchrotron radiation. The astounding advances in the science and technology of semiconductor heterostructures have been made possible by three fundamental achievements: The density of the electron system at the interface can be effectively tuned by virtue of band structure engineering; the mobility of charge carriers doped into interface states which exceeds the bulk mobility by orders of magnitude; and the carriers which can channel into patterned devices along the interface. All three conditions have recently been replicated in heterostructures of complex transition metal oxides. As complex oxide materials exhibit a remarkably rich phase behavior in the bulk, quantum states with properties and functionalities beyond those attainable in semiconductors are expected to emerge in the interface-controlled oxides. Based on this, the project to fabricate, explore and thoroughly understand new quantum phenomena that arise at the oxide interfaces due to nanoscale effects and artificially broken symmetries is proposed. Using the atomic layer-by-layer synthesis the physics at the interface between non-Fermi liquid correlated metals and Mott insulators will be explored. Quantum coherence in the systems where interfacial magnetism and high-Tc superconductivity can co-exist will be investigated. Recently predicted new quantum phenomena such as exotic magnetic states and orbital reconstruction at the superconductor/ferromagnet interface will be sought out. New artificial quantum crystals that are tailored for properties not attainable in the bulk will be fabricated and explored. For this purpose, resonant soft X-ray spectroscopies and polarized neutrons at major national facilities and international centers of excellence will be utilized. Based on this proposal, a new graduate course in experimental methods for nanoscience and a new outreach summer program - "Nano-Camp" will be specifically developed for underrepresented students and minorities across Arkansas. The proposed research will be used as a hub for the popular NSF GK-12 and REU programs.
Modern achievements in microelectronics rely on the properties of interfaces between two different semiconductors and the knowledge about electronic phenomena near semiconductor interfaces. Recent advances in the growth of oxides now allow for the formation of sharp boundaries between the atomic layers of complex oxides materials. Given the rich properties in the bulk of these compounds due to strong interactions between the electrons, the new interface quantum states promise the opportunity to uncover unexpected phenomena. The goal of this project is to fabricate and explore what are called artificial quantum materials with engineered physical properties not attainable in the bulk. X-rays synchrotron radiation that scatters from the spin, charge and orbit of an electron will provide unique knowledge about the behavior of the electrons at the interfaces. Understanding and manipulating these properties will open a path towards a new generation of oxide based electronic devices. Based on this proposal, a new graduate course in experimental methods for nanoscience and a new outreach summer program - "Nano-Camp" will be specifically developed for underrepresented students and minorities across Arkansas. This project will also serve as a hub for stocking the emerging field with future scientists and engineers and will help to maintain a competitive presence in science and technology.
Broader scientific impacts: In general, the project was focused on developing a novel framework for smart materails by rational design, where the main "instrument" is the interface between dissimilar layers of complex oxides with correlated electrons. First, the PI uncovered a novel, correlated-electron behavior emerging at the interface between high Tc superconducting YBa2Cu3O7/ferromagnetic LaCaMnO3 and Mott insulator/band insulator due to the possibility that such interfacial phenomena can form the basis for a new group of nanomaterials with greatly enhanced functionality. Specifically, the PI has demonstrated that magnetic structure at the interface are critical for determining the macroscopic properties of the overall superconductor/ferromagnet system; here by using polarized neutron reflectrometry for the first time the PI has quantitatively determined the interfacial magnetization structure. By application of synchortron based Xray spectroscopies the PI delivered the very first microscopic insight into the interplay of spin and orbital degrees of freedom at the interface resulting in the spin reconstruction phenomenon at both cuprate and manganite atomic planes at the interface. Most intriguing, the PI has demonstrated the presence of ferromagnetic moments inside the superconducting state, which changed the traditional point of view of high temepertaure cuprates. The devised methodology has been established as an incisive probe of the interplay between competing electronic order parameters in oxide heterostructures. The discovery of magnetic electrons in the interfacial cuprate layer (i.e. the inverse proximity effect) is of fundamental importance for spintronic applications. Resonant X-ray experiments with linearly polarized light further uncovered the unprecedented ability of the interface to manipulate atomic orbitals, the PI has coined a new term - orbital reconstruction at the interface, which is now a standard toolkit for the interface physics. The project established that the interface provides fertile ground for discovery of new electronic phenomena having potential for the next generation of devices based on spin degree of freedom and possibly future quantum computing application. Broader Educational and Outreach Impacts: One of the most important outcomes of the proposal is based on understanding that the emerging field of interfaces of artificial quantum materials is on the verge of breakthrough, and the educational activities associated with the proposal will be critical to laying the groundwork for stocking the field with scientists and engineers and will help the US maintain a competitive presence in science and technology. To promote science and critical thinking among general public, including frequent open house visits (4 times per year), co-organizing a popular "Hunted Physics House" during Halloween for kids and active development of the State wide IGERT conference for undergraduate students to attract as many as possible students which are traditionally underrepresented in hard sciences. The newly developed class on "Experimental Methods on Nanoscience" and "NANO-CAMP" program is another important educational activity for the State and beyond. The multimedia program on exotic properties of materials ("Crazy Materials") distributed via the Internet will allow for broader educational impact reaching larger audience. In collaboration with the Office for Public Relation and the Multimedia Lab of UofA, the PI has been developing a bi-weekly podcast preliminary called "Ask physicist a question", with the concept to provide a brief 3-5 minute question-answer podcast on "hot" physics and specifically nanoscience discoveries. The podcast will be made available on YouTube and on the UofA website (e.g., www.youtube.com/watch?v=zMGCVdnLte8). Additionally, the PI has successfully produced and dissimilated a high Tc superconductivity show-and-tell kit to local Arkansas wide school science teachers.
