Temperature and Doping-Dependent Renormalization Effects of the Low Energy Electronic Structure of Ba1-xKxFe2As2 Single Crystals

We investigate the low energy electronic structure of Ba1-xKxFe2As2 (x=0; 0.3, T-c=32 K) single crystals by angle-resolved photoemission spectroscopy with a focus on the renormalization of the dispersion. A kink feature is detected at E approximate to 25 meV for the doped compound which vanishes at T=200 K but stays virtually constant when T-c is crossed. Our experimental findings rule out the magnetic resonance mode as the origin of the kink and render conventional electron-phonon coupling unlikely. They put stringent restrictions on the dominant source of the electronic interaction channel.