Quasiparticle coherence in nematic state studied with strain-dependent ARPES

The microscopic mechanism of nematicity in iron-based superconductors is still unresolved. Most models consider either spin or orbital degrees as driving force but typically do not take electronic correlations into account. However, the interplay of Coulomb interactions and Hund’s rule coupling leads to observable bad metallic behavior, orbital-dependent mass renormalizations and an overall suppression of quasiparticle coherence. We studied the influence of nematic order on the quasiparticle coherence in BaFe₂As₂ using strain-dependent ARPES and compare them to our results on detwinned FeSe. Inside the nematic phase, we find an anisotropy of the spectral weight between the d_xz and the d_yz orbitals in the coherent quasiparticle peak and in the incoherent Hubbard band. We interpret our results in terms of a more coherent d_xz orbital compared to the d_yz orbital. Our study highlights the importance of electronic correlations in the description of nematicity in iron-based superconductors.