Theoretical evidence for strong correlations and incoherent metallic state in FeSe

The role of electronic Coulomb correlations in iron-based superconductors is an important open question. We provide theoretical evidence for strong correlation effects in FeSe, based on dynamical mean field calculations. Our ab initio spectral properties first demonstrate the existence of a lower Hubbard band. Moreover, together with significant orbital-dependent mass enhancements, we find that the normal state is a bad metal over an extended temperature range, implying a non-Fermi liquid due to formation of local moments. Predictions for angle-resolved photoemission spectroscopy are made.