Superconductivity without a hole pocket in electron-doped FeSe: Analysis beyond the Migdal-Eliashberg formalism

Article

关键词: IRON-BASED SUPERCONDUCTORS;    NEMATICITY;    SRTIO3;    FILMS;    LAYER;    CHALCOGENIDES;    FRUSTRATION;    SYMMETRY;   

DOI  :  10.1103/PhysRevB.96.045130

来源: SCIE

【 摘 要 】

High-T-c pairing mechanism absent of hole pockets in heavily electron-doped FeSe is one of the key unsolved problems in Fe-based superconductors. Here, this problem is attacked by focusing on the higher-ordermany-body effects neglected in conventional Migdal-Eliashberg formalism. We uncover two significant many-body effects for high-T-c superconductivity. (i) Due to the vertex correction, the dressed multiorbital Coulomb interaction acquires prominent orbital dependence for low-energy electrons. The dressed Coulomb interaction not only induces the orbital fluctuations, but also magnifies the electron-boson coupling constant. Therefore, moderate orbital fluctuations give strong attractive pairing interaction. (ii) The multi-fluctuation-exchange pairing process causes large interpocket attractive force, which is as important as the usual single-fluctuation-exchange process. Due to these two significant effects dropped in the Migdal-Eliashberg formalism, the anisotropic s(++)-wave state in heavily electron-doped FeSe is satisfactorily explained. The proposed inter-electron-pocket pairing mechanism will enlarge T-c in other Fe-based superconductors.

【 授权许可】

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