Absence of Superconductivity in the "hole-doped" Fe pnictide Ba(Fe$_{1-x}$Mn$_{x}$)$_{2}$As$_{2}$: Photoemission and X-ray Absorption Spectroscopy Studies

Abstract: We have studied the electronic structure of Ba(Fe${1-x}$Mn${x}$)${2}$As${2}$ ($x$=0.08), which fails to become a superconductor in spite of the formal hole doping like Ba${1-x}$K${x}$Fe${2}$As${2}$, by photoemission spectroscopy and X-ray absorption spectroscopy (XAS). With decreasing temperature, a transition from the paramagnetic phase to the antiferromagnetic phase was clearly observed by angle-resolved photoemission spectroscopy. XAS results indicated that the substituted Mn atoms form a strongly hybridized ground state. Resonance-photoemission spectra at the Mn $L_{3}$ edge revealed that the Mn 3d partial density of states is distributed over a wide energy range of 2-13 eV below the Fermi level ($E_F$), with little contribution around $E_F$. This indicates that the dopant Mn 3$d$ states are localized in spite of the strong Mn 3d-As $4p$ hybridization and split into the occupied and unoccupied parts due to the on-site Coulomb and exchange interaction. The absence of superconductivity in Ba(Fe${1-x}$Mn${x}$)${2}$As${2}$ can thus be ascribed both to the absence of carrier doping in the FeAs plane, and to the strong stabilizaiton of the antiferromagnetic order by the Mn impurities.