A. Toschi

Wien2wannier: From linearized augmented plane waves to maximally localized Wannier functions

Abstract We present an implementation of an interface between the full-potential linearized augmented plane wave package Wien2k and the wannier90 code for the construction of maximally localized Wannier functions. The FORTRAN code and a documentation is made available and results are discussed for SrVO 3 , Sr 2 IrO 4 (including spin–orbit coupling), LaFeAsO, and FeSb 2 .

Dynamical vertex approximation — a step beyond dynamical mean field theory

Institute of Metal Physics, 620219 Ekaterinburg, Russia(Dated: Version 8, February 6, 2008)We develop a diagrammatic approach with local and nonlocal self-energy diagrams, constructedfrom the local irreducible vertex. This approach includes the local correlations of dynamical meanfield theory and long-range correlations beyond. It allows for example to describe (para-)magnonsand weak localization effects—in strongly correlated systems. As a first application, we study theinterplay between nonlocal antiferromagnetic correlations and the strong local correlations emergingin the vicinity of a Mott-Hubbard transition.

Dichotomy between Large Local and Small Ordered Magnetic Moments in Iron-Based Superconductors

We study a four-band model for iron-based superconductors within the local density approximation combined with dynamical mean-field theory (LDA+DMFT). This successfully reproduces the results of models which take As p degrees of freedom explicitly into account and has several physical advantages over the standard five d-band model. Our findings reveal that the new superconductors are more strongly correlated than their single-particle properties suggest. Two-particle correlation functions unveil the dichotomy between local and ordered magnetic moments in these systems, calling for further experiments to better resolve the short time scale spin dynamics.

Inequivalent routes across the Mott transition in V2O3 explored by X-ray absorption.

The changes in the electronic structure of V2O3 across the metal-insulator transition induced by temperature, doping, and pressure are identified using high resolution x-ray absorption spectroscopy at the V pre-K edge. Contrary to what has been taken for granted so far, the metallic phase reached under pressure is shown to differ from the one obtained by changing doping or temperature. Using a novel computational scheme, we relate this effect to the role and occupancy of the a{1g} orbitals. This finding unveils the inequivalence of different routes across the Mott transition in V2O3.

Local electronic correlation at the two-particle level

Electronic-correlated systems are often well described by dynamical mean field theory (DMFT). While DMFT studies have mainly focused hitherto on one-particle properties, valuable information is also enclosed into local two-particle Greens functions and vertices. They represent the main ingredient to compute momentum-dependent response functions at the DMFT level and to treat nonlocal spatial correlations at all length scales by means of diagrammatic extensions of DMFT. The aim of this paper is to present a DMFT analysis of the local reducible and irreducible two-particle vertex functions for the Hubbard model in the context of a unified diagrammatic formalism. An interpretation of the observed frequency structures is also given in terms of perturbation theory, of the comparison with the atomic limit, and of the mapping onto the attractive Hubbard model.

Pseudogap of metallic layered nickelate R(2-x)Sr(x)NiO4 (R = Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy.

We have investigated charge dynamics and electronic structures for single crystals of metallic layered nickelates, R(2-x)Sr(x)NiO4 (R = Nd, Eu), isostructural to La(2-x)Sr(x)CuO4. Angle-resolved photoemission spectroscopy on the barely metallic Eu(0.9)Sr(1.1)NiO4 (R = Eu, x = 1.1) has revealed a large hole surface of x2-y2 character with a high-energy pseudogap of the same symmetry and comparable magnitude with those of underdoped (x<0.1) cuprates, although the antiferromagnetic interactions are 1 order of magnitude smaller. This finding strongly indicates that the momentum-dependent pseudogap feature in the layered nickelate arises from the real-space charge correlation.

Comparing pertinent effects of antiferromagnetic fluctuations in the two and three dimensional Hubbard model

We use the dynamical vertex approximation

Conserved quantities of S U ( 2 ) -invariant interactions for correlated fermions and the advantages for quantum Monte Carlo simulations

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Electronics with Correlated Oxides: SrVO(3)/SrTiO(3) as a Mott Transistor.

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Fate of the false Mott-Hubbard transition in two dimensions

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