%0 Journal Article
%T Functional renormalization group study of the pairing symmetry and pairing mechanism in iron-selenide superconductors
%A Yuan-Yuan Xiang
%A Yang Yang
%A Wan-Sheng Wang
%A Zheng-Zao Li
%A Qiang-Hua Wang
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevB.88.104516
%X In iron selenide superconductors only electron-like Fermi pockets survive, challenging the $S^{\pm}$ pairing based on the quasi-nesting between the electron and hole Fermi pockets (as in iron arsenides). By functional renormalization group study we show that an in-phase $S$-wave pairing on the electron pockets ($S^{++}_{ee}$) is realized. The pairing mechanism involves two competing driving forces: The strong C-type spin fluctuations cause attractive pair scattering between and within electron pockets via Cooperon excitations on the virtual hole pockets, while the G-type spin fluctuations cause repulsive pair scattering. The latter effect is however weakened by the hybridization splitting of the electron pockets. The resulting $S^{++}_{ee}$-wave pairing symmetry is consistent with experiments. We further propose that the quasiparticle interference pattern in scanning tunneling microscopy and the Andreev reflection in out-of-plane contact tunneling are efficient probes of in-phase versus anti-phase $S$-wave pairing on the electron pockets.
%U http://arxiv.org/abs/1305.1806v2