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Register a new userCombined GW and dynamical mean field theory: Dynamical screening effects in transition metal oxides
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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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A combination of dynamical mean field theory and density functional theory, as implemented in Phys. Rev. B 81, 195107 (2010), is applied to both the early and late transition metal oxides. For fixed value of the local Coulomb repulsion, without fine tuning, we obtain the main features of these series, such as the metallic character of SrVO$_3$ and the the insulating gaps of LaVO$_3$, LaTiO$_3$ and La$_2$CO$_4$ which are in good agreement with experiment. The study highlights the importance of local physics and high energy hybridization in the screening of the Hubbard interaction and how different low energy behaviors can emerge from the a unified treatment of the transition metal series.
The dynamical mean-field theory (DMFT) is a widely applicable approximation scheme for the investigation of correlated quantum many-particle systems on a lattice, e.g., electrons in solids and cold atoms in optical lattices. In particular, the combination of the DMFT with conventional methods for the calculation of electronic band structures has led to a powerful numerical approach which allows one to explore the properties of correlated materials. In this introductory article we discuss the foundations of the DMFT, derive the underlying self-consistency equations, and present several applications which have provided important insights into the properties of correlated matter.
A metal-insulator transition (MIT) in BiFeO$_3$ under pressure was investigated by a method combining Generalized Gradient Corrected Local Density Approximation with Dynamical Mean-Field Theory (GGA+DMFT). Our paramagnetic calculations are found to be in agreement with experimental phase diagram: Magnetic and spectral properties of BiFeO3 at ambient and high pressures were calculated for three experimental crystal structures $R3c$, $Pbnm$ and $Pmbar{3}m$. At ambient pressure in the $R3c$ phase, an insulating gap of 1.2 eV was obtained in good agreement with its experimental value. Both $R3c$ and $Pbnm$ phases have a metal-insulator transition that occurs simultaneously with a high-spin (HS) to low-spin (LS) transition. The critical pressure for the $Pbnm$ phase is 25-33 GPa that agrees well with the experimental observations. The high pressure and temperature $Pmbar{3}m$ phase exhibits a metallic behavior observed experimentally as well as in our calculations in the whole range of considered pressures and undergoes to the LS state at 33 GPa where a $Pbnm$ to $Pmbar{3}m$ transition is experimentally observed. The antiferromagnetic GGA+DMFT calculations carried out for the $Pbnm$ structure result in simultaneous MIT and HS-LS transitions at a critical pressure of 43 GPa in agreement with the experimental data.
In this Letter we report the first LDA+DMFT (method combining Local Density Approximation with Dynamical Mean-Field Theory) results of magnetic and spectral properties calculation for paramagnetic phases of FeO at ambient and high pressures (HP). At ambient pressure (AP) calculation gave FeO as a Mott insulator with Fe 3$d$-shell in high-spin state. Calculated spectral functions are in a good agreement with experimental PES and IPES data. Experimentally observed metal-insulator transition at high pressure is successfully reproduced in calculations. In contrast to MnO and Fe$_2$O$_3$ ($d^5$ configuration) where metal-insulator transition is accompanied by high-spin to low-spin transition, in FeO ($d^6$ configuration) average value of magnetic moment $sqrt{<mu_z^2>}$ is nearly the same in the insulating phase at AP and metallic phase at HP in agreement with X-Ray spectroscopy data (Phys. Rev. Lett. {bf83}, 4101 (1999)). The metal-insulator transition is orbital selective with only $t_{2g}$ orbitals demonstrating spectral function typical for strongly correlated metal (well pronounced Hubbard bands and narrow quasiparticle peak) while $e_g$ states remain insulating.
We present a new methodology to solve the Anderson impurity model, in the context of dynamical mean-field theory, based on the exact diagonalization method. We propose a strategy to effectively refine the exact diagonalization solver by combining a finite-temperature Lanczos algorithm with an adapted version of the cluster perturbation theory. We show that the augmented diagonalization yields an improved accuracy in the description of the spectral function of the single-band Hubbard model and is a reliable approach for a full d-orbital manifold calculation.
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