ARPES of K-doped iron selenide superconductor

In iron pnictide superconductors, the characteristic Fermi surface(FS) topology, namely nesting of hole-like FS at the zone center and electron-like FS at the zone corner, is considered to induce spin/orbital fluctuation leading to high-Tc superconductivity [1,2]. In K-doped iron selenide superconductors, however, ARPES studies reported absence of hole-like FS at the zone center, which is different from that observed in iron pnictides [3]. So far, proposed models for the superconductivity based on the FS topology appear to fail to explain available experimental results. In this talk, we present our recent ARPES studies on a K-doped iron selenide superconductor performed with careful tuning of experimental conditions, which show a hole-like FS around the zone center. [1] I. I. Mazin et al., Phys. Rev. Lett. 101, 057003 (2008); K. Kuroki et al., Phys. Rev. Lett. 101, 087004 (2008). [2] H. Kontani et al., Phys. Rev. Lett. 104, 157011 (2010). [3] Y. Zhang et al., Nat. Mater. 10, 273 (2011); T. Qian et al., Phys. Rev. Lett. 106, 187001 (2011).