Cover：Fermi surface of (Tl, Rb)_xFe_2-ySe₂ superconductor as revealed by high resolution angle-resolved photoemission spectroscopy.  Two electron-like Fermi surface sheets are observed around the central point while one electron-like Fermi surface sheet is observed around the zone corner M point which is actually composed of two degenerate Fermi surface sheets. Such Fermi surface topology is distinct from that of other iron-based superconductors. It provides key insight on understanding the pairing mechanism in the iron-based superconductors. More details could be found in the article “Structural, magnetic and electronic properties of the iron－chalcogenide A_xFe_2-ySe₂ (A=K, Cs, Rb, and Tl, etc.) superconductors” by Dai-xiang Mou, Lin Zhao, and Xing-jiang Zhou, pp 410－428. [Photo credits: Xing-jiang Zhou, Institute of Physics, Chinese Academy of Sciences, China]

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