Fernando Assis Garcias, Ames National Laboratory

Incoherent electronic band states in Mn substituted BaFe₂As₂

Partial chemical substitution is commonly used to trigger and explore new ground states in electronic correlated materials. The main effect of the substitution is usually rationalized in terms of electron/hole doping and/or chemical pressure. The role of disorder, which is intrisic to this strategy, is often overlooked.  In Mn-substituted  BaFe₂As₂ (MnBFA), Mn is a putative nominal hole dopant to the parent compound.  Superconductivity (SC), however, is absent, despite being observed for nominal hole-doped BaFe₂As₂ phases. In this seminar, we shall present a comprehensive investigation of the MnBFA electronic structure  using angle-resolved photoemission spectroscopy (ARPES).   We find that, to a large extent, electron and hole states remain nested and that Mn mainly increases the incoherence of the MnBFA electronic bands, showing that substitutional disorder dominates over electronic doping. Our results allows a comprehensive understanding for the absence of SC in MnBFA and explains the glassy character of the MnBFA magnetism. We will also discuss data for Cr-substituted   BaFe₂As₂, which shows that the effect of transition metal substitution is very specific, with Cr behaving more as hole dopant than Mn.