Dynamical Magnetism in Superconducting and Non-Superconducting 11 Iron Chalcogenides

There are profound connections between dynamical magnetism and unconventional superconductivity in Fe-based superconductors. Recently, new aspects associated with their multi-band, multi-orbital nature and the resulting orbital physics came to prominence in the iron chalcogenide family. Neutron scattering experiments revealed signatures of an orbital-selective electron localization and ferro-orbital order in the FeTe parent material. In the superconducting iron chalcogenide materials, the ARPES studies discovered significant temperature- and orbital-dependent correlation effects in the electronic band structure that are indicative of orbital-selective Mott physics. More recently, an orbital-selective Cooper pairing was discovered in the FeSe end member by STM. Here, we present polarized neutron scattering studies of magnetic dynamics in Fe_1+yTe_1-xSe_x samples with and without superconductivity. We analyze the evolution of the wave-vector dependence of the dynamical magnetic scattering with temperature and composition in order to understand the nature of magnetic and orbital electronic states arising from the orbital-selective correlation effects.