The origin of the condensation energy scaling of iron-based superconductors

Abstract

The relation between the condensation energy (CE) and Tc of a phase transition reveals a fundamental nature of the transition. In view of this, the recent experimental observation of the non-BCS scaling relation of the CE vs. with about forty different samples of the Fe-based superconductors (Xing J. et al., Phys. Rev. B, 89 (2014) 140503) was intriguing and strongly hinted at a non-BCS pairing mechanism. In this paper, we have studied the CE and Tc of the multiband BCS model and found that the observed anomalous scaling relation is well reproduced by the two-band BCS model paired by a dominant repulsive interband interaction . Our result implies that this seemingly non-BCS–like scaling behavior of , on the contrary to the common expectations, is in fact a strong experimental evidence that the pairing mechanism of the Fe-based superconductors is genuinely a BCS mechanism, meaning that the Cooper pairs are formed by the itinerant carriers glued by a pairing interaction.