  Deviations of low-energy electronic structure of iron-based superconductors
from density functional theory predictions have been parametrized in terms of
band- and orbital-dependent mass renormalizations and energy shifts. The former
have typically been described in terms of a local self-energy within the
framework of dynamical mean field theory, while the latter appears to require
non-local effects due to interband scattering. By calculating the renormalized
bandstructure in both random phase approximation (RPA) and the two-particle
self-consistent approximation (TPSC), we show that correlations in pnictide
systems like LaFeAsO and LiFeAs can be described rather well by a non-local
self-energy. In particular, Fermi pocket shrinkage as seen in experiment occurs
due to repulsive interband finite-energy scattering. For the canonical iron
chalcogenide system FeSe in its bulk tetragonal phase, the situation is however
more complex since even including momentum-dependent band renormalizations
cannot explain experimental findings. We propose that the long-range Coulomb
interaction may play an important role in band-structure renormalization in
FeSe. We further compare our evaluations of non-local quasiparticle scattering
lifetime within RPA and TPSC with experimental data for LiFeAs.
