CM seminar - Orbital-selectivity and nematicity in iron-chalcogenide superconductors

Abstract: Electron correlation effects give rise to a variety of emergent phenomena in quantum materials-high temperature superconductivity, electronic nematicity, Mott insulating phase, and magnetism. In the multi-orbital iron-based superconductors, electronic correlations are manifested in an orbital-dependent way, realizing all of the above in different parameter regimes. In this talk, I will present experimental evidence from angle-resolved photoemission spectroscopy on systematic evolution of multi-orbital correlation effects across the iron-based superconductor material basis. In particular, I will present spectroscopic evidence for tendencies towards an orbital-selective Mott phase in Fe(Te,Se) as tuned via both temperature and isovalent substitution, as manifested in the modification of the Fermiology accompanied by the vanishing of coherent quasiparticle spectral weight and the divergence of effective mass. I will also present a connection to the role of orbitals in the nematic phase of FeSe. These exotic behaviors reveal the strong presence of correlation effects in this class of multi-orbital superconductors.