Orbital-Selective Mottness in Layered Iron Oxychalcogenides: The Case of Na_{2}Fe_{2}OSe_{2}

Abstract: Using a combination of th local-density approximtion (LDA) and dynamicla mean-field theory (DMFT) calculations, we explore the correlated electronic structure of a member of the layered Iron oxychalcogenide Na_{2}Fe_{2}OSe_{2}. We find that the parent compund is a multi-orbital Mott insulator. Surprisingly, and somewhat reminiscent of the doped high-T_{c} cuprates, carrier localization is found to persist upon weak hole doping because the chemical potential lies in a gap structure wit almost vanishing density-of-states (DOS). On the other hand, in remarkable contrast, electron doping drives an orbital-selective metallic phase (OSMP) with co-existing pseudogapped (Mott localized) and itinerant carriers. These remarkably contrasting behaviors in a single system thus stem from drastic electronic reconstruction caused by large-scale transfe of dynamical spectral weightinvolving states with distinct orbital character at low energies, putting the Fe oxychalcogenidesneatly into the increasingly visible tendency of Fe-baed systems as ones in orbital-selective Mott phases. We detail the implications of our analysis, and discuss the nature and symmetry of the superconductive states that may arise upon proper doping or pressurizing Na_{2}Fe_{2}OSe_{2}.