Temperature-dependent pseudogap in the oxypnictides LaFeAsO1-x Fx and LaFePO1-x Fx seen via angle-integrated photoemission

We have performed a temperature-dependent angle-integrated laser photoemission study of iron oxypnictide superconductors LaFeAsO:F and LaFePO:F exhibiting critical-transition temperatures (Tc 's) of 26 and 5 K, respectively. We find that high- Tc LaFeAsO:F exhibits a temperature-dependent pseudogaplike feature extending over ∼0.1 eV about the Fermi level at 250 K, whereas such a feature is absent in low- Tc LaFePO:F. We also find ∼20-meV pseudogaplike features and signatures of superconducting gaps in both LaFeAsO:F and LaFePO:F. We discuss the possible origins of the unusual pseudogaplike features through comparison with the high- Tc cuprates.