Atomic-Scale Heterostructures of Iridates and Ruthenates

Non-Technical Description:

This project investigates atomic-scale quantum materials composed of iridium oxides and ruthenium oxides. Both materials have attracted great attention due to their competing physical parameters. Tuning the parameters is expected to be the key to advancing the electronic and magnetic states of matter targeting new quantum technologies, but experimentally realizing the tunability is a difficult task.

This project addresses exactly that point by synthesizing a new model system in which two oxides can interact with each other in an ideal two-dimensional interface. The project also investigates microscopic properties and structures using advanced spectroscopy and microscopy. These research activities relate to education for both graduate and undergraduate students.

The United States desperately needs professionals with strong expertise in advanced material synthesis and characterization for both the tech industry and academia. Participating students receive state-of-the-art material synthesis training and work with scientists from National Labs. It provides an essential opportunity for students to develop their careers.

The project also raises science awareness among non-STEM majors via a summer research program for prospective teachers and visiting classrooms at local public schools in Kentucky, either in person or online. These outreach activities not only provide a unique research experience to share, but also raise awareness of cutting-edge science in general.

Technical Description:

The project investigates the two-dimensional interface between iridates and ruthenates, where strong spin-orbit interactions (SOI) and electron-correlations (U) coexist. Whereas tuning the parameters of U and SOI in condensed matter is expected to provide nontrivial states, the experimental realization of tunable U and SOI is a formidable task. The project’s atomic-scale epitaxial heterostructure approach offers a tool to control the dimensionality and the lattice-symmetry through strong interactions at a two-dimensional interface.

The confluence of U and SOI of the 5d and 4d extended orbitals at the interface is expected to exhibit an unprecedented electromagnetic state. Since these new heterostructures can stabilize metastable quantum phases as their interactions are varied, the project explores the theoretically predicted phase diagrams of exotic ground states. Hence, the results of this project fill the existing gap between experiment and theory, allowing a better understanding of the strongly correlated and spin-orbit-coupled electrons in condensed matter.

To this end, the project uses pulsed laser deposition with in-situ real-time monitoring techniques to develop various epitaxial heterostructures of iridates and ruthenates. Experimental characterization includes advanced spectroscopy and microscopy such as infrared spectroscopy, resonance elastic/inelastic X-ray scattering, and high-resolution transmission electron microscopy.

Participating students gain expertise in advanced material synthesis and characterization techniques. The project also raises awareness of science through summer research programs and outreach for local public schools in Kentucky.

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.