  We present detailed LDA'+DMFT investigation of doping dependence of
correlation effects in novel K{1-x}Fe{2-y}Se2 superconductor. Calculations were
performed at four different hole doping levels, starting from hypothetical
stoichiometric composition with total number of electrons equal to 29 per unit
cell through 28 and 27.2 electrons towards the case of 26.52, which corresponds
to chemical composition K{0.76}Fe{1.72}Se2 studied in recent ARPES experiments.
In general case the increase of hole doping leads to quasiparticle bands in
wide energy window +/-2 eV around the Fermi level becoming more broadened by
lifetime effects, while correlation induced compression of Fe-3d LDA'
bandwidths stays almost the same and of the order of ~1.3 for all hole
concentrations. However close to the Fermi level situation is more complicated.
Here in the energy interval from -1.0 eV to 0.4 eV the bare Fe-3d LDA' bands
are compressed by significantly larger renormalization factors up to 5 with
hole doping increase, while the value of Coulomb interaction remains the same.
This fact manifests the increase of correlation effects with hole doping in
K{1-x}Fe{2-y}Se2 system. Moreover in contrast to typical pnictides
K{1-x}Fe{2-y}Se2 does not have well defined quasiparticle bands on the Fermi
leves but pseudogap like "dark" region instead. We also find that with the
growth of hole doping Fe-3d orbitals of various symmetries are affected by
correlations in a different way in different parts of Brillouin zone. To
illustrate this we determine quasiparticle mass renormalization factors and
energy shifts, which transform the bare Fe-3d LDA' bands of various symmetries
into LDA'+DMFT quasiparticle bands. These renormalization factors effectively
mimic more complicated energy dependent self-energy effects and can be used to
analyze the available ARPES data.
