Many-body effects in iron pnictides and chalcogenides -- non-local vs dynamic origin of effective masses

We apply the quasi-particle self-consistent GW (QS{\it GW}) approximation to some of the iron pnictide and chalcogenide superconductors. We compute Fermi surfaces and density of states, and find excellent agreement with experiment, substantially improving over standard band-structure methods. Analyzing the QS{\it GW} self-energy we discuss non-local and dynamic contributions to effective masses. We present evidence that these two contributions are mostly separable. Indeed the quasi-particle weight is found to be essentially independent of momentum. The main effect of non-locality is captured by the static but non-local QSGW effective potential. Moreover, these non-local self-energy corrections, absent in e.g.\ dynamical mean field theory (DMFT), can be relatively large. We show, on the other hand, that QS{\it GW} only partially accounts for dynamic renormalizations at low energies. These findings suggest that QS{\it GW} combined with DMFT will capture most of the many-body physics in the iron pnictides and chalcogenides.\\[4pt] Reference: Jan M. Tomczak, M. van Schilfgaarde, G. Kotliar, PRL accepted, preprint: arXiv:1209.2213