Disorder and the Emergence of Inhomogeneous Phases in Strongly Correlated Electron Systems

University Of Florida, Gainesville FL

Investigators

Abstract

NON-TECHNICAL SUMMARY This award supports research and education designed to advance our understanding of materials containing mobile electrons that interact strongly with each other, giving rise to new states of matter with novel superconductive properties. Superconductivity is a quantum state of many electrons in a metal that is characterized by the loss of electrical resistance and consequently of all dissipation of energy. The materials to be investigated include cuprate and Fe-based superconductors, as well as iridate systems. The PI's group will use model calculations for electrons to study several problems directed towards a broader understanding of how these materials work. In particular the fundamental physics of defects and impurities that can destroy or nucleate superconducting states under different circumstances will be studied. These investigations will result in a deeper understanding of the nature of high temperature superconductivity. Understanding properties of correlated electron systems and the influence of disorder may lead to novel materials properties that could be utilized in new devices and technologies, obtaining unusual sensitivity operating near transitions between competing phases that occur in highly correlated electron systems. This could have enormous technological implications. The award will support training of graduate students. The PI's group will engage in outreach activities to educate schoolchildren in the Gainesville area about physics, hold public and colloquium talks on superconductivity, and offer information on research activities at a public level through the extensive website. TECHNICAL SUMMARY This award supports theoretical research and education to address long-standing fundamental problems of quenched disorder and various types of competing emergent order in correlated electron systems. The materials to be investigated include cuprate and Fe-based superconductors, as well as iridate systems. The Fe-based superconductors exhibit a wide variety of behavior suggesting that the electronic responses to external perturbations that break xy symmetry are extremely strong, and may be important for superconductivity. Both electron-doped cuprate superconductors and Fe-based superconductors exhibit phases where itinerant spin density wave order coexists with superconductivity. Properties of electronic states in these materials will be studied through a careful analysis of simplified models of interacting electrons on the lattice, informed in some cases by microscopic density functional theory calculations. The PI's group will also study the influence of impurities on electronic nematic instabilities in Fe-based superconducting systems at temperatures above the superconducting transition. To achieve research goals the full numerical and analytical calculations of the superconducting critical temperature and order parameter in the Hubbard model across its phase diagram, including the spin density wave and coexistence phases within a fluctuation exchange interaction approximation will be performed.