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Abstract Understanding characteristic energy scales is a fundamentally important issue in the study of strongly correlated systems. In multiband systems, an energy scale is affected not only by the effective Coulomb interaction but also by the Hund’s coupling. Direct observation of such energy scale has been elusive so far in spite of extensive studies. Here, we report the observation of a kink structure in the low energy dispersion of NiS 2− x Se x and its characteristic evolution with x , by using angle resolved photoemission spectroscopy. Dynamical mean field theory calculation combined with density functional theory confirms that this kink originates from Hund’s coupling. We find that the abrupt deviation from the Fermi liquid behavior in the electron self-energy results in the kink feature at low energy scale and that the kink is directly related to the coherence-incoherence crossover temperature scale. Our results mark the direct observation of the evolution of the characteristic temperature scale via kink features in the spectral function, which is the hallmark of Hund’s physics in the multiorbital system.

Correction for ‘Measured and simulated thermoelectric properties of FeAs 2−x Se x ( x = 0.30–1.0): from marcasite to arsenopyrite structure’ by Christopher J. Perez et al. , Mater. Adv. , 2020, 1 , 1390–1398, DOI: 10.1039/D0MA00371A.

Iron diantimonide is a material with the highest known thermoelectric power. By combining scanning transmission electron microscopic study with electronic transport neutron, X-ray scattering, and first principle calculation, we identify atomic defects that control colossal thermopower magnitude and nanoprecipitate clusters with Sb vacancy ordering, which induce additional phonon scattering and substantially reduce thermal conductivity. Defects are found to cause rather weak but important monoclinic distortion of the unit cellPnnm → Pm. The absence of Sb along [010] for high defect concentration forms conducting path due to Fedorbital overlap. The connection between atomic defect anisotropy and colossal thermopower in FeSb₂paves the way for the understanding and tailoring of giant thermopower in related materials.