Nodal Superconductivity with Multiple Gaps in SmFeAsO$_{0.9}$F$_{0.1}$

TL;DR

This study reveals multiple superconducting gaps and nodal behavior in SmFeAsO$_{0.9}$F$_{0.1}$, supported by spectroscopic evidence and theoretical BCS-like temperature dependence, indicating unconventional superconductivity.

Contribution

First observation of multiple gaps and nodal superconductivity in F-SmFeAsO using point-contact spectroscopy, highlighting its unconventional nature.

Findings

Two superconducting gaps observed that vanish at $T_c$

Presence of Andreev bound states indicated by ZBCP

Gaps follow BCS temperature dependence

Abstract

We report the observation of two gaps in the superconductor SmFeAsO$_{0.9}$F$_{0.1}$ (F-SmFeAsO) with $T_c=51.5K$ as measured by point-contact spectroscopy. Both gaps decrease with temperature and vanish at $T_c$ and the temperature dependence of the gaps are described by the theoretical prediction of the Bardeen-Cooper-Schrieffer (BCS) theory. A zero-bias conductance peak (ZBCP) was observed, indicating the presence of Andreev bound states at the surface of F-SmFeAsO. Our results strongly suggest an unconventional nodal superconductivity with multiple gaps in F-SmFeAsO.