Emergence of Fully-Gapped $s_{++}$-wave and Nodal d-wave States Mediated by Orbital- and Spin-Fluctuations in Ten-Orbital Model for KFe${}_2$Se${}_2$

Tetsuro Saito, Seiichiro Onari, Hiroshi Kontani

We study the superconducting state in newly discovered high-Tc superconductor K${}_x$Fe${}_2$Se${}_2$ based on the ten-orbital Hubbard-Holstein model without hole-pockets. When the Coulo…