Quantum Heterostructures of Rhodates and Iridates with Tunable Electron-Correlation and Spin-Orbit Interactions

Project Summary Overview: This proposal aims to investigate quantum heterostructures comprised of 4d rhodates and 5d iridates, where both systems exhibit intriguing convergence due to comparable energy scales of electron- correlation (U) and spin-orbit interaction (SOI) inherent in the 4d and 5d orbitals. While manipulating U and SOI parameters in condensed matter promises a captivating model system for generating nontrivial electronic and magnetic properties, achieving experimental control over these tunable parameters poses significant challenges. This proposal’s concept is to explore heterointerfaces, where 4d and 5d electrons can strongly interact across ideal two-dimensional interfaces. Recent studies and our own preliminary data indicate that rhodate/iridate heterointerfaces exhibit notable charge transfer and long-range coupling of U and SOI, leading to unconventional exchange interactions and electronic band structures. A fundamental question arises: “What microscopic mechanisms underlie the emergence of these states?” To address this question, we will examine heterostructure samples as a model system. Our primary focus is on obtaining experimental evidence of novel electronic and magnetic states by characterizing our samples using advanced spectroscopic techniques such as resonant inelastic X-ray scattering, Raman spectroscopy, and infrared spectroscopic ellipsometry. Additionally, we aim to develop comprehensive frameworks for understanding the strong interfacial interactions of U and SOI between 4d and 5d electrons. Intellectual Merit: The confluence of U and SOI in 4d and 5d electronic systems may give rise to exotic ground states, potentially revolutionizing our comprehension of fundamental condensed matter physics. Existing experimental methodologies for investigating these systems necessitate a novel tool capable of adjusting the physical parameters. The quantum heterostructure approach outlined in this proposal is deemed suitable for establishing a model system wherein exotic ground states of strongly-correlated, spin-orbit coupled electrons can emerge. This method enables tunability in controlling dimensionality and lattice symmetry through strong interactions at two-dimensional interfaces. By manipulating spin-orbit interaction and electron-correlation, the extended orbitals of 4d and 5d electrons may manifest unprecedented electromagnetic states. As these artificial heterointerfaces stabilize metastable quantum phases under varying parameters, this approach provides a means to explore phase diagrams. The outcomes of this project will bridge the existing gap between condensed matter experiments and theories in 4d and 5d transition-metal oxides, leading to a deeper understanding of strongly-correlated, spin-orbit coupled electrons in condensed matter systems. The preliminary results from the PI’s group demonstrate their ability to produce high-quality epitaxial heterostructure samples of rhodates and iridates, marking a crucial initial step in this project. Broader Impacts: The proposed research endeavors are intricately linked with the education of both graduate and undergraduate students. There exists a pressing demand for experimental condensed matter physicists with robust expertise in advanced materials synthesis and characterization in the United States, across academia and industry. To address this need, the PI will impart education and training to students in state-of-the-art materials synthesis techniques and facilitate opportunities for collaboration with scientists at National Labs, thereby enhancing their prospects for success in their careers. Moreover, the PI places great importance on nurturing the scientific literacy of younger generations, particularly in science and technology fields. To this end, initiatives will include establishing a research summer program tailored for pre-service teachers and conducting in-person outreach visits to local high school classrooms in Kentucky. These outreach endeavors aim not only to provide a unique research experience to share but also to cultivate a deeper appreciation for the advancement of cutting-edge science among participants.