Microscopic description of localization-delocalization transitions in BaFe2S3

We present a microscopic description of electronic reconstruction in BaFe2S3, a system which undergoes a pressure-induced insulator-metal transition followed by a superconducting phase at 24 K. We stress the importance of multiorbital electron-electron interactions for a consistent understanding of its intrinsic Mott-insulating and pressurized, orbital-selective metallic normal states. We explain the first-order nature of the Mott transition, showing that it is driven by dynamical spectral weight transfer in response to changes in the on-site Coulomb interaction to bandwidth ratio. As a by-product of this analysis, we unearth how dynamical correlations underpin spectroscopy and resistivity responses, in good agreement with experiment. Upon electron/hole doping, carrier localization is found to persist because the chemical potential lies in a gap structure with vanishing states near the Fermi energy. We detail the implications of our microscopic analysis for the underlying physics which emerges in the normal state of a compressed BaFe2S3 superconductor.