Orbital-dependent electron dynamics in Fe-pnictide superconductors

We report on orbital-dependent quasiparticle dynamics in EuFe2As2, a parent compound of Fe-based superconductors, and a way to experimentally identify this behavior using time- and angle-resolved photoelectron spectroscopy across the spin density wave transition. We observe two different relaxation timescales for photoexcited dxz/dyz and dxy electrons. While the itinerant dxz/dyz electrons relax faster through the electron-electron scattering channel, dxy electrons form a quasiequilibrium state with the lattice due to their localized character, and the state decays slowly. Our findings suggest that electron correlation in Fe pnictides is an important property, which should carefully be taken into account when describing the electronic properties of both parent and carrier-doped compounds, and therefore establish a strong connection with cuprates. © 2018 American Physical Society.