This IRG aims to discover the coupling mechanisms between oxygen defects and the transport of phonons, spin and charge at the interfaces of metal oxides, with transformative implications for energy and informationtechnologies. Recent investigations of novel electronic and magnetic properties of complex oxide superlattices have led to tantalizing discoveries. A prime example is the high mobility metallic state found at the interfaces of LaAlO3/SrTiO3 superlattices, composed of materials both of which individually are insulating. The study of the confinement of electrons at these interfaces, and superlattices generally, has had an extraordinary impact on our understanding of important phenomena that can enable high electron mobility devices. Now, a tremendous opportunity exists to achieve further breakthroughs in understanding the role of confinement near oxide interfaces on ionic defect stability and mobility, an area previously defined as nanoionics. Although many structural and electronic factors are known to affect interface properties, we believe oxygen defects play a central role in these phenomena, but their role has thus far been under-explored. While the study of the charge transport behavior of ionic materials at the nanoscale has been pursued for the past decade, this project extends these efforts into entirely new directions by offering means to manipulate and couple the transport of ions, charge, phonons, and magnetic spin.
This ability will enable novel energy-relevant devices such as electrically controlled heat valves, and high efficiency energy conversion platforms such as thermoelectrics and fuel cells, as well as high density and fast memory and logic computing platforms such as memristive and magnetoelectronic devices. Our proposal brings forth two key attributes that set this IRG apart from the existing field of defect studies in oxides. First is the novel and cross-disciplinary merging of nanoionics, phononics, magnetics and electrochemistry, which offers fertile ground for many scientific discoveries by examining the interrelated behavior of ionic defects, charge, spin and phonons. This capacity confers the ability to tune the defect chemistry and ion transport, and to examine their impact in a coupled manner on charge, spin and phonon transport, and magnetic properties. Second is the suite of new capabilities developed by the PIs in this IRG, integrating novel synthesis of nanoscale superlattices characterized by vertical and lateral interfaces, in situ characterization, and multiscale modeling and simulation from the atomic to the mesoscale. By in situ characterization, we mean the ability to perform measurements with very high spatial and temporal resolution in the presence of elevated temperatures (up to ~1000 °C), high electric fields and chemically reactive gases. This approach to identify and interpret, for example, phonon scattering, strain induced oxygen diffusion, and defect induced magnetization at interfaces, presents a powerful predictive capability for designing new materials.