부산대학교 도서관

We carried out high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of K0.68Fe1.79Se2 (Tc=32 K) and (Tl0.45K0.34)Fe1.84Se2 (Tc=28 K) superconductors. In addition to the electron-like Fermi surface near M(π,π), two electron-like Fermi pockets are revealed around the zone center Γ(0,0) in K0.68Fe1.79Se2. This observation makes the Fermi surface topology of K0.68Fe1.79Se2 consistent with that of (Tl, Rb)xFe2-ySe2 and (Tl, K)xFe2-ySe2 compounds. A nearly isotropic superconducting gap Δ is observed along the electron-like Fermi pocket near the M point in K0.68Fe1.79Se2 (Δ∼9 meV) and (Tl0.45K0.34)Fe1.84Se2 (Δ ∼ 8 meV). The establishment of a universal picture on the Fermi surface topology and superconducting gap in the AxFe2-ySe2 (A=K, Tl, Cs, Rb, etc.) superconductors will provide important information for understanding the superconductivity mechanism of iron-based superconductors. [ABSTRACT FROM AUTHOR]