Metal-insulator transitions and symmetry breaking in spin-orbit Mott materials

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Nontechnical Abstract: The goal of this project is to study the electronic and structural properties of crystalline materials found at a new frontier of condensed matter physics, one where materials possess both an appreciable interaction between electrons in tandem with a strong coupling between their inherent magnetism (spin) and their orbital motion. This unique combination of energy scales is predicted to stabilize fundamentally new states of electronic matter, ranging from new forms of superconductivity to new quantum entangled states with far-term applications potential in quantum computing. Research supported by the project focuses on understanding the materials pathways necessary for realizing these new states and on exploring the interactions responsible for driving the prototypical parent state of these materials - the spin-orbit Mott phase - from an insulator into a metal. Supported activities work to train the next generation of scientists utilizing national neutron and x-ray user facilities as well as work to address the nation's growing deficit in new materials discovery/synthesis by supporting the growth of new crystalline materials. The project provides research experience to undergraduates from underrepresented demographics through summer research internships as well as conducts outreach activities aimed at inspiring precollege students to pursue materials science/physics academic and career pathways. Technical Abstract: The project focuses on experimentally exploring the mechanisms through which new classes of spin-orbit Mott (SOM) materials are driven from their parent insulating states into the metallic regime via carrier/bandwidth tuning. The insulating phases of SOM systems are inherently driven by a delicate interplay between strong spin-orbit coupling, crystal field, and short-range Coulomb interactions. This unique balance of energy scales in SOM compounds is predicted to host nearby exotic ground states ranging from high temperature superconductivity, to novel forms of quantum spin liquids, to correlated topological phases. Models of these new phases place them within close proximity to the parent SOM state. The primary goal of the project is to understand how interactions evolve once this parent state is destabilized and driven into nearby materials phase space - specifically, to resolve the role of electron correlations and the evolution of electronic and structural degrees of freedom as the metallic state is approached. Searching for new states/phase behaviors beyond the melting of the spin-orbit Mott phase is a second, overlapping goal of the supported research. Research activities are comprised of a combined materials synthesis, bulk electron properties characterization, and neutron/x-ray scattering effort aimed at forming a comprehensive picture of interactions in perturbed SOM states in classes of Ruddlesden-Popper, pyrochlore, and geometrically frustrated iridates. Students at the graduate and undergraduate levels will be trained in materials synthesis techniques as well as in the use of neutron and x-ray scattering at national user facilities, helping to build the core of the next generation of the national user community.