Effect of band filling in the paramagnetic tetragonal phase of iron chalcogenides

The normal state of layered Fe-chalcogenide superconductors shows a range of anomalous, non-Fermi liquid responses. Unconventional metallic resistivity, characteristic pseudogap and saturating features and proximity to insulating states mark these systems as correlated metals. Motivated thereby, we use a combination of first-principles and many-particle calculations to show that multiband electronic correlations generate a low-energy pseudogap in the normal state of Fe(Te,Se) end-members, which, depending on the band filling, promotes incoherent metallic or orbital-selective insulating states. Upon comparison, good qualitative agreement with experimental (photoemission and electrical resistivity) data of FeTe_1−xSe _x systems is found. Based on observed charge transport we propose that the parent bulk compounds are best described as partially filled multiband systems. (paper)