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Maria Fuglsang Jensen - Laboratoire de Physique des Solides d’Orsay

ARPES study of the antiferromagnetic phase of BaFe2As2

Since the recent discovery of iron-based superconductors, the relationship between magnetism and superconductivity has been a central question. A better understanding of the nature of the magnetic state, especially its itinerant or localized origin, is needed to go further. I will present an angle-resolved photoemission study of the electronic structure of BaFe2As2 in its paramagnetic and antiferromagnetic (AFM) phases. The analysis of the changes at the transition are rather complex to decipher, because there are many different bands crossing the Fermi level, leading to a complex Fermi surface of multi-orbital nature. Strong variations of the intensity of the different bands as a function of photon energy and/or photon polarization are observed, emphasizing one band or the other in different experimental conditions. I will present data measured in different experimental conditions, which allow to resolve two bands constituting the electron pockets, with clearly different orbital symmetries. They build an elliptic electron pocket, which is imperfectly nested with the circular hole pockets. This explains the formation of residual metallic pockets in the AFM phase. In addition, we observed shifts of numerous bands at the transition, which indicate a redistribution of the orbital occupations. Some of these shifts are sensitive to the surface structure. I will discuss the respective role of dxz/dyz and of the other orbitals in the electronic structure reorganization at the AFM transition.


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