Dynamical Magnetism and Orbital Selective Physics in 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 iron the chalcogenide family. While early neutron scattering experiments already presented indication of an orbital-selective electron localization and ferro-orbital order in the FeTe parent material [1,2], an orbital-selective Cooper pairing was recently discovered in the FeSe end member by STM [3]. Here, we present polarized neutron scattering studies of magnetic dynamics in FeTe parent material and FeTe_0.45Se_0.55 optimally doped superconductor, where we analyze the wave vector dependence of the magnetic form factor in order to understand the orbital state of magnetic electrons. Our results indicate an unusual, energy- and temperature-dependent orbital composition of dynamical magnetism revealed by polarized neutron spectroscopy.
[1] I. A. Zaliznyak, et. al., Phys. Rev. Lett. 107, 216403 (2011).
[2] D. Fobes, et. al., Phys. Rev. Lett. 112, 187202 (2014).
[3] P. O. Sprau, et al, Science 357, 75-80 (2018).