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      Combined GW and dynamical mean field theory: Dynamical screening effects in transition metal oxides

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          Abstract

          We present the first dynamical implementation of the combined GW and dynamical mean field scheme ("GW+DMFT") for first principles calculations of the electronic properties of correlated materials. The application to the ternary transition metal oxide SrVO3 demonstrates that this schemes inherits the virtues of its two parent theories: a good description of the local low energy correlation physics encoded in a renormalized quasi-particle band structure, spectral weight transfer to Hubbard bands, and the physics of screening driven by long-range Coulomb interactions. Our data is in good agreement with available photoemission and inverse photoemission spectra; our analysis leads to a reinterpretation of the commonly accepted "three-peak structure" as originating from orbital effects rather than from the electron addition peak within the t2g manifold.

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          Maximally-localized generalized Wannier functions for composite energy bands

          We discuss a method for determining the optimally-localized set of generalized Wannier functions associated with a set of Bloch bands in a crystalline solid. By ``generalized Wannier functions'' we mean a set of localized orthonormal orbitals spanning the same space as the specified set of Bloch bands. Although we minimize a functional that represents the total spread sum_n [ _n - _n^2 ] of the Wannier functions in real space, our method proceeds directly from the Bloch functions as represented on a mesh of k-points, and carries out the minimization in a space of unitary matrices U_mn^k describing the rotation among the Bloch bands at each k-point. The method is thus suitable for use in connection with conventional electronic-structure codes. The procedure also returns the total electric polarization as well as the location of each Wannier center. Sample results for Si, GaAs, molecular C2H4, and LiCl will be presented.
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            Frequency-dependent local interactions and low-energy effective models from electronic structure calculations

            We propose a systematic procedure for constructing effective models of strongly correlated materials. The parameters, in particular the on-site screened Coulomb interaction U, are calculated from first principles, using the GW approximation. We derive an expression for the frequency-dependent U and show that its high frequency part has significant influence on the spectral functions. We propose a scheme for taking into account the energy dependence of U, so that a model with an energy-independent local interaction can still be used for low-energy properties.
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              Mott transition and suppression of orbital fluctuations in orthorhombic 3\(d^{1}\) perovskites

              Using \(t_{2g}\) Wannier-functions, a low-energy Hamiltonian is derived for orthorhombic \(3d^{1}\) transition-metal oxides. Electronic correlations are treated with a new implementation of dynamical mean-field theory for non-cubic systems. Good agreement with photoemission data is obtained. The interplay of correlation effects and cation covalency (GdFeO\(_{3}\)-type distortions) is found to suppress orbital fluctuations in LaTiO\(_{3},\) and even more in YTiO\(_{3}\), and to favor the transition to the insulating state.
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                Author and article information

                Journal
                24 October 2012
                2012-12-18
                Article
                10.1209/0295-5075/100/67001
                1210.6580
                f16141a3-0176-45a6-8660-091e6940fa81

                http://arxiv.org/licenses/nonexclusive-distrib/1.0/

                History
                Custom metadata
                EPL (Europhysics Letters) 100, 67001 (2012)
                replaced with published version (6 pages, 3 figures); first version was submitted to PRL on June 19, 2012
                cond-mat.str-el cond-mat.mtrl-sci

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