Functional renormalization group study of pairing symmetry and pairing mechanism in iron-selenide superconductors

Abstract

In iron-selenide superconductors, only electronlike Fermi pockets survive, challenging the S± pairing based on the quasinesting between the electron and hole Fermi pockets (as in iron arsenides). We performed a functional renormalization group study and showed that an in-phase S-wave pairing on the electron pockets (See++) 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 See++-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 antiphase S-wave pairing on the electron pockets.

Source-reported materials — not catalogue approval

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