Multiple gaps in SmFeAsO0.9F0.1 revealed by point-contact spectroscopy

We report the observation of two gaps in the superconductor SmFeAsO0.9F0.1 (F-SmFeAsO) with T-c = 51.5 K as measured by point-contact spectroscopy. Both gaps decrease with temperature and vanish at Tc, and the temperature dependence of the gaps is described by the theoretical prediction of the Bardeen-Cooper-Schrieffer (BCS) theory. A zero-bias conductance peak (ZBCP) was observed, indicating the presence of sign reversal of the gap function in F-SmFeAsO. Our results strongly suggest an unconventional superconductivity with multiple gaps in F-SmFeAsO.