Strong Electron Correlations in the Normal State of the Iron-Based FeSe0.42Te0.58 Superconductor Observed by Angle-Resolved Photoemission Spectroscopy

We investigate the normal state of the 11'' iron-based superconductor FeSe0.42Te0.58 by angle-resolved photoemission. Our data reveal a highly renormalized quasiparticle dispersion characteristic of a strongly correlated metal. We find sheet dependent effective carrier masses between approximate to 3 and 16m(e) corresponding to a mass enhancement over band structure values of m*/m(band) approximate to 6-20. This is nearly an order of magnitude higher than the renormalization reported previously for iron-arsenide superconductors of the 1111'' and 122'' families but fully consistent with the bulk specific heat.