Effect of Li-deficiency impurities on the electron-overdoped LiFeAs superconductor

Abstract

We use transport, inelastic neutron scattering, and angle-resolved photoemission experiments to demonstrate that the stoichiometric LiFeAs is an intrinsically electron-overdoped superconductor similar to those of the electron-overdoped NaFe${}_{1\ensuremath{-}x}{T}_{x}$As and BaFe${}_{2\ensuremath{-}x}{T}_{x}$As${}_{2}$ ($T=\text{Co}$, Ni). Furthermore, we show that although transport properties of the stoichiometric superconducting LiFeAs and Li-deficient nonsuperconducting Li${}_{1\ensuremath{-}x}$FeAs are different, their electronic and magnetic properties are rather similar. Therefore, the nonsuperconducting Li${}_{1\ensuremath{-}x}$FeAs is also in the electron overdoped regime, where small Li deficiencies near the FeAs octahedra can dramatically suppress superconductivity through the impurity scattering effect.