ARPES studies of the iron pnictide superconductors

A lot of progress has been made in understanding the family of iron-based pnictide superconductors since its discovery. However, many issues still remain. Here we use angle-resolved photoemission to study the electronic structures of various pnictide materials. Specifically, through a systematic high-resolution study of the parent compounds (Ba,Sr)Fe$_{2}$As$_{2}$, we show that the electronic structures of these materials are significantly reconstructed across the spin density wave transition, which cannot be described by a simple folding scenario of conventional density wave ordering. Moreover, we find that LDA calculations with an incorporated suppressed magnetic moment of 0.5$\mu _{B}$ can match well the details in the reconstructed electronic structure, suggesting that the nature of magnetism in the pnictides is more itinerant than local, while the origin of suppressed magnetic moment remains an important issue for future investigations.