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Understanding the Fermi surface and low-energy excitations of iron or cobalt pnictides is crucial for assessing electronic instabilities such as magnetic or superconducting states. Here, we propose and implement a new approach to compute the low-energy properties of correlated electron materials, taking into account both screened exchange beyond the local density approximation and local dynamical correlations. The scheme allows us to resolve the puzzle of BaCo2As2, for which standard electronic structure techniques predict a ferromagnetic instability not observed in nature.
We derive an analytical expression for the local two-particle vertex of the Falicov-Kimball model, including its dependence on all three frequencies, the full vertex and all reducible vertices. This allows us to calculate the self energy in diagramma
In terms of the state-of-the-art first principle computational methods combined with the numerical renormalization group technique the spectroscopic properties of Co adatoms deposited on silicene are analyzed. By establishing an effective low-energy
In the framework of cluster perturbation theory for the 2D Hubbard and Hubbard-Holstein models at low hole doping we have studied the effect of local and short-range correlations in strongly correlated systems on the anomalous features in the electro
We have measured the optical conductivity of single crystal LuMnO3 from 10 to 45000 cm-1 at temperatures between 4 and 300 K. A symmetry allowed on-site Mn $d$-$d$ transition near 1.7 eV is observed to blue shift (~0.1 eV) in the antiferromagnetic st
While second-order phase transitions always cause strong non-local fluctuations, their effect on spectral properties crucially depends on the dimensionality. For the important case of three dimensions, we show that the electron self-energy is well se