Materials with strong electronic correlations have long resisted abinitio modeling due to their complexity arising from non-perturbative strength of the interaction. The Dynamical Mean Field Theory in combination with the Density Functional Theory has recently changed this position, and enabled detailed modeling of the electronic structure of many complex materials, such as the heavy fermions, transition metal oxides, iron superconductors, etc.  I will give basic foundation of this theory from the functional point of view, and an overview on the recent advances in this field.  As an example, I will discuss the iron superconductors and their anomalous properties, which have their origin in strong Hund's coupling and give rise to reach physics of Hund's metals. I will show how Dynamical Mean Field Theory simulations not only uncovered the origin of the anomalous properties, but also successfully explained 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, and the magnetic excitations in energy and momentum space. The ab-initio simulations of the two particle verte function allowed the study of the spin dynamics and superconducting pairing symmetry, and a novel orbital antiphase s+− symmetry was proposed, which has been missed by both the weak and the strong coupling approaches, as it is driven by Hund's coupling in metallic systems.  This orbital-antiphase pairing symmetry explains the puzzling variation of the experimentally observed superconducting gaps on all the Fermi surfaces of LiFeAs, and may be realized in other iron superconductors.

Understanding correlated electron materials: The insight from the functional dynamical mean field approach

251st National Meeting (2016)

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