CAREER: Emergent Phases of Correlated Electrons in Materials with Spin-Orbit Coupling and Magnetic Frustration

TECHNICAL SUMMARY

This award supports theoretical on novel quantum phases that arise from the collective behavior of correlated electrons in the presence of strong spin-orbit coupling and frustration. The main focus is on 5d transition metal oxides, such as iridates and osmates, in which spin-orbit-coupling is comparable to, or larger than Coulomb energy. Specific 5d transition metal oxide systems have recently attracted a lot of theoretical and experimental attention because of unusual hierarchy of interactions, extended nature of 5d-orbitals, and high sensitivity to crystal fields. Because of these properties 5d systems are candidate materials for the realization of various emergent quantum phases, such as spin liquids, topological insulators, Weyl semimetals, and novel magnetically ordered Mott insulators.

The PI aims to develop and analyze effective spin-orbital models which describe the low-energy physics of correlated systems in the presence of strong spin-obit coupling. The PI plans to study the ground state phase diagrams of these models and identify the nature of possible quantum states and phase transitions with an emphasis on studying finite temperature properties of these models, as the presence of anisotropic interactions in these models significantly affects the nature of finite temperature phase transitions. The PI will also study the effects of doping, as this can give rise to high-temperature superconductivity in these systems.

Another thrust of the research is devoted to the analysis of elementary excitations in systems with strong spin-orbit-coupling. The PI plans to use a new computational framework to study quasiparticles in the magnetically ordered ground state in materials with strong spin-orbit-coupling, which she has recently developed. The method is quite useful for interpreting data obtained by the resonant inelastic x-ray scattering, which currently is the most effective tool to study the dispersion of elementary magnetic excitations across the whole Brillouin zone. The PI will also apply the method to analyze the effects of strong spin-orbit-coupling in Raman scattering from iridates and osmates. The PI?s ultimate goal is to provide a better understanding and description of existing experimental data and to generate verifiable predictions for future experiments.

This project will be carried out in collaboration with collaborators from Europe and Japan. The collaboration brings an international dimension to the education of graduate students involved in the project. The PI plans to develop an advanced course in strongly correlated phenomena in complex materials and systems with special emphasis on new trends in magnetism and transport phenomena. In collaboration with other local faculty, the PI will create a Wisconsin Winter School on Modern Condensed Matter and Quantum Information and will organize short-term courses of condensed matter physics. This Winter School will introduce young researchers to various specific problems in the field and will also improve collaboration between faculty, students, and postdocs from different campuses of the University of Wisconsin System. The PI will also deliver a series of annual lectures for High School students and Physics lectures and seminars in support of the physics department outreach activity. The lectures will include the topics of quantum mechanics, computer science, and the future of material science.

NONTECHNICAL SUMMARY

This award supports theoretical and computational research and educational activities aimed at advancing our understanding of materials, in which the electron spin, an intrinsic quantum mechanical property of electrons, and the motion of the electron in a material strongly interact with each other, known as the spin-orbit interaction. The relevant materials are oxides that include transition metals, specifically iridium and osmium, in which the way the atoms are organized in space leads to a spin or spatial distribution of electrons which can occur in many nearly equivalent and hence, competing ways. The PI will focus on the case where the spin-orbit interaction dominates the familiar Coulomb interaction between electrons that arises from the electron charge. Achieving a theoretical understanding of the resulting properties of these materials in which the interactions among electrons lead to strong correlations in their motions is challenging. Interest in these systems stems in part from the richness of their novel properties: the unexpected variety of ways the electrons organize themselves, which leads, for example, to various forms of magnetism, the transformations among these states, and new phenomena that can arise in these iridium and osmium bearing materials. The PI will use theoretical and computational methods to investigate the physical properties of these transition metal oxides, predict new effects in these materials, and contribute to understanding the intriguing results of experiments.

This project will be carried out in collaboration with collaborators from Europe and Japan. The collaboration brings an international dimension to the education of graduate students involved in the project. The PI plans to develop an advanced course in strongly correlated phenomena in complex materials and systems with special emphasis on new trends in magnetism and transport phenomena. In collaboration with other local faculty, the PI will create a Wisconsin Winter School on Modern Condensed Matter and Quantum Information and will organize short-term courses of condensed matter physics. This Winter School will introduce young researchers to various specific problems in the field and will also improve collaboration between faculty, students, and postdocs from different campuses of the University of Wisconsin System. The PI will also deliver a series of annual lectures for High School students and Physics lectures and seminars in support of the physics department outreach activity. The lectures will include the topics of quantum mechanics, computer science, and the future of material science.