Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 54: Focused Session: Magnetism & Superconductivity in Fe-based Pnictides and Chalcogenides (jointly with MA)

TT 54.2: Hauptvortrag

Donnerstag, 14. März 2013, 10:00–10:30, H20

Electron Correlations in Solids from the Dynamical Mean Field Perspective and the Origin Anomalous State of Matter in Iron Chalchogenides — •Kristjan Haule — Rutgers The State University of New Jersey, Piscataway, NJ, USA

The Dynamical Mean Field Theory in combination with the Density Functional Theory has recently enabled detailed modeling of the electronic structure of complex materials such as heavy fermions, transition metal oxides, chalchogenides and arsenides. Simulations based on this method has recently uncovered the origin of unusual properties of iron based high temperature superconductors and the physics behind the poor metallic conductivity in these systems. Here the Coulomb interaction among the electrons is not strong enough to localize electrons, but it significantly slows them down, such that low-energy emerging quasiparticles have a substantially enhanced mass, and at intermediate temperature and intermediate energy scale show strong deviations from the Fermi liquid theory. This enhanced mass emerges not because of the Hubbard interaction U, but because of the Hund's rule interactions J that tends to align electrons with the same spin but different orbital quantum numbers when they find themselves on the same atom. The ab-initio simulations with the Dynamical Mean Field Theory not only uncover the origin of anomalous properties, but also successfully explains the key properties of these material: such as the mass renormalizations and anisotropy of quasiparticles, the crossover into an incoherent regime above a low temperature scale, the magnetic moments in iron compunds, and dispersion of magnetic excitations.