Momentum dependent electron and hole dynamics and electron-phonon coupling in iron pnictides from time- and angle-resolved photoemission spectroscopy

The Fe pnictide parent compound EuFe2As2 and the doped BaFe1.85Co0.15As2 high-Tc super- conductor exhibit a strongly momentum dependent dynamics of states around the hole pocket at the center of the Brillouin zone. Electrons and holes show different dynamics which cannot be explained solely by intraband scattering, but interband contributions have to be considered. In addition, three coherently excited modes at frequencies of 5.6, 3.3 and 2.6 THz are observed. An estimate of the electron-phonon coupling parameter reveals lambda < 0.5, suggesting a limited importance of e-ph coupling to superconductivity in Fe pnictides.