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Common Fermi-surface topology and nodeless superconducting gap of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">K</mml:mi><mml:mrow><mml:mn>0</mml:mn><mml:mo>.</mml:mo><mml:mn>68</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Fe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mo>.</mml:mo><mml:mn>79</mml:mn></mml:mrow></mml:…
We carried out high resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of K_0.68Fe_1.79Se_2 (T_c=32 K) and (Tl_0.45K_0.34)Fe_1.84Se_2 (T_c=28 K) superconductors. In addition to the electron-like Fermi surface near M(\pi,\pi), two electron-like Fermi pockets are revealed around the zone center \Gamma(0,0) in K0.68Fe1.79Se_2. This observation makes the …