Electronic Structure of the BaFe$_2$As$_2$ Family of Iron Pnictides

Abstract

We use high resolution angle-resolved photoemission spectroscopy to study the band structure and Fermi surface topology of the BaFe$_2$As$_2$ iron pnictides. We observe two electron bands and two hole bands near the X-point, $(\pi,\pi)$ of the Brillouin zone, in the paramagnetic state for different doping levels, including electron-doped Ba(Co$_{0.06}$Fe$_{0.94}$)$_2$As$_2$, undoped BaFe$_2$As$_2$, and hole-doped Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$. Among these four bands, only the electron bands cross the Fermi level, forming two electron pockets around X, while the hole bands approach but never reach the Fermi level. We show that the band structure of the BaFe$_2$As$_2$ family matches reasonably well with the prediction of LDA calculations after a momentum-dependent shift and renormalization. Our finding resolves a number of inconsistencies regarding the electronic structure of pnictides.