In: Physical Review D, 2014, vol. 90, no. 6, p. 065008
We review the extended mean field theory (EMFT) approximation and apply it to complex, scalar φ4 theory on the lattice. We study the critical properties of the Bose condensation driven by a nonzero chemical potential μ at both zero and nonzero temperature and determine the (T,μ) phase diagram. The results are in very good agreement with recent Monte Carlo data for all parameter values...

In: Physical Review D, 2013, vol. 88, no. 12, p. 125006
We apply the dynamical mean field theory (DMFT) approximation to the real, scalar φ4 quantum field theory. By comparing to lattice Monte Carlo calculations, perturbation theory and standard mean field theory, we test the quality of the approximation in two, three, four and five dimensions. The quantities considered in these tests are the critical coupling for the transition to the ordered phase...

In: Physical Review Letters, 2012, vol. 109, no. 20, p. 206401
We calculate the phase diagram of the BoseFermi Hubbard model on the 3d cubic lattice at fermionic half filling and bosonic unit filling by means of singlesite dynamical meanfield theory. For fast bosons, this is equivalent to the Cooper problem in which the bosons can induce swave pairing between the fermions. We also find miscible superfluid and canted supersolid phases depending on the...

In: Reviews of Modern Physics, 2014, vol. 86, no. 2, p. 779–837
The study of nonequilibrium phenomena in correlated lattice systems has developed into one of the most active and exciting branches of condensed matter physics. This research field provides rich new insights that could not be obtained from the study of equilibrium situations, and the theoretical understanding of the physics often requires the development of new concepts and methods. On the...

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 twodimensional Hubbard model with onsite and nearestneighbor repulsion. We clarify the relation of the GW+DMFT scheme to alternative approaches in the literature, and discuss the corresponding approximations to the freeenergy functional of the model. Furthermore, we describe a numerically...

In: Physical Review B, 2017, vol. 95, no. 24, p. 245130
In electronic systems with longrange Coulomb interaction, the nonlocal Fock exchange term has a bandwidening effect. While this effect is included in combined manybody 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...

In: Physical Review Letters, 2012, vol. 109, no. 22, p. 226401
We present a fully selfconsistent combined GW and dynamical mean field (DMFT) study of the extended twodimensional Hubbard model. The inclusion of the local dynamical vertex stemming from the DMFT selfenergy and polarization is shown to cure the known problems of selfconsistent GW. We calculate momentumresolved spectral functions, twoparticle polarizations, and electronloss spectra, as...

In: Physical Review X, 2015, vol. 5, no. 3, p. 031039
Symmetrybroken states such as magnetic order and superconductivity are the hallmark of complex properties in solids. An intriguing new direction in condensedmatter physics is to manipulate these properties on the fastest possible time scales using ultrashort laser pulses. Theoretically, however, the collective manyparticle dynamics that is responsible for the formation and melting of...

In: Physical Review B, 2020, vol. 101, no. 8, p. 085127
We investigate the effect of nonlocal interactions on the photodoped Mott insulating state of the twodimensional Hubbard model using a nonequilibrium generalization of the dynamical cluster approximation. In particular, we compare the situation where the excitonic states are lying within the continuum of doublonholon excitations to a setup where the excitons appear within the Mott gap. In...

In: Physical Review B, 2016, vol. 94, no. 20, p. 201106
The cubic perovskite SrVO3 is generally considered to be a prototype strongly correlated metal with a characteristic threepeak structure of the delectron spectral function, featuring a renormalized quasiparticle band in between pronounced Hubbard sidebands. Here we show that this interpretation, which has been supported by numerous “ab initio” simulations, has to be reconsidered. Using...
