Multiple gaps in SmFeAsO_0.9F_0.1revealed by point-contact spectroscopy

Abstract

We report the observation of two gaps in the superconductor SmFeAsO0.9F0.1 (F–SmFeAsO) with Tc = 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.