Université de Fribourg

Influence of Fock exchange in combined many-body perturbation and dynamical mean field theory

Ayral, Thomas ; Biermann, Silke ; Werner, Philipp ; Boehnke, Lewin

In: Physical Review B, 2017, vol. 95, no. 24, p. 245130

In electronic systems with long-range Coulomb interaction, the nonlocal Fock- exchange term has a band-widening effect. While this effect is included in combined many-body perturbation theory and dynamical mean field theory (DMFT) schemes, it is not taken into account in standard extended DMFT (EDMFT) calculations. Here, we include this instantaneous term in both approaches and investigate its...

Université de Fribourg

Tuning electronic correlations in transition metal pnictides: Chemistry beyond the valence count

Razzoli, Elia ; Matt, Christian E. ; Kobayashi, M. ; Wang, X.-P. ; Strocov, V. N. ; Roekeghem, A. van ; Biermann, Silke ; Plumb, N. C. ; Radovic, M. ; Schmitt, T. ; Capan, C. ; Fisk, Z. ; Richard, P. ; Ding, H. ; Aebi, Philipp ; Mesot, J. ; Shi, Ming

In: Physical Review B, 2015, vol. 91, no. 21, p. 214502

The effects of electron-electron correlations on the low-energy electronic structure and their relationship with unconventional superconductivity are central aspects in the research on iron-based pnictide superconductors. Here we use soft x-ray angle-resolved photoemission spectroscopy to study how electronic correlations evolve in different chemically substituted iron pnictides. We find that...

Université de Fribourg

Extended dynamical mean-field study of the Hubbard model with long-range interactions

Huang, Li ; Ayral, Thomas ; Biermann, Silke ; Werner, Philipp

In: Physical Review B, 2014, vol. 90, no. 19, p. 195114

Using extended dynamical mean-field theory and its combination with the GW approximation, we compute the phase diagrams and local spectral functions of the single-band extended Hubbard model on the square and simple cubic lattices, considering long-range interactions up to the third nearest neighbors. The longer-range interactions shift the boundaries between the metallic, charge-ordered...

Université de Fribourg

Screening and nonlocal correlations in the extended Hubbard model from self-consistent combined GW and dynamical mean field theory

Ayral, Thomas ; Biermann, Silke ; Werner, Philipp

In: Physical Review B, 2013, vol. 87, no. 12, p. 125149

We describe a recent implementation of the combined GW and dynamical mean field method (GW+DMFT) for the two-dimensional Hubbard model with onsite and nearest-neighbor repulsion. We clarify the relation of the GW+DMFT scheme to alternative approaches in the literature, and discuss the corresponding approximations to the free-energy functional of the model. Furthermore, we describe a numerically...

Université de Fribourg

Spectral Properties of Correlated Materials: Local Vertex and Nonlocal Two-Particle Correlations from Combined GW and Dynamical Mean Field Theory

Ayral, Thomas ; Werner, Philipp ; Biermann, Silke

In: Physical Review Letters, 2012, vol. 109, no. 22, p. 226401

We present a fully self-consistent combined GW and dynamical mean field (DMFT) study of the extended two-dimensional Hubbard model. The inclusion of the local dynamical vertex stemming from the DMFT self-energy and polarization is shown to cure the known problems of self-consistent GW. We calculate momentum-resolved spectral functions, two-particle polarizations, and electron-loss spectra, as...