Far-infrared probe of superconductivity in SmO1 xFxFeAs

The discovery of high Tc superconductivity in the iron pnictides(1) has provoked a vivid debate concerning the microscopic origin of superconductivity in these 3d tran- sition metal compounds. Motivated by the fact that elec- tron correlation effects play a dominant role in the phys- ical properties of 3d transition metals, it is believed that the pairing interaction in the iron pnictides is mediated by coupling to spin-fluctuations as opposed to phonons (2, 3, 4, 5, 6).