Evolution of the band structure of superconducting NaFeAs from optimally doped to heavily overdoped Co substitution using angle-resolved photoemission spectroscopy

Abstract

Using angle-resolved photoemission spectroscopy, we studied the evolution of electronic structure of NaFe${}_{1\ensuremath{-}x}$Co${}_{x}$As from an optimally doped superconducting compound ($x=0.028$) to a heavily overdoped nonsuperconducting one ($x=0.109$). As in ``122''-type iron pnictides, our data suggest that the Co dopant in NaFe${}_{1\ensuremath{-}x}$Co${}_{x}$As supplies extra charge carriers and shifts the Fermi level accordingly. The overall band renormalization remains basically the same throughout the doping range we studied, suggesting that the local magnetic and electronic correlations are not affected by carrier doping. In the $x=0.109$ compound, the holelike bands around the zone center $\ensuremath{\Gamma}$ move to deeper binding energies and an electron pocket appears instead, resulting in a Fermi surface topology similar to that of $A$${}_{x}$Fe${}_{2\ensuremath{-}y}$Se${}_{2}$ ($A=\mathrm{K}$, Cs, Rb, Tl). Our data suggest that a balance between itinerant properties of mobile carriers and local interactions plays an important role for the superconductivity in these materials.