title: Ca2O3Fe2.6S2: an antiferromagnetic Mott insulator at proximity to bad metal.
abstract: We report here the first layered iron oxychalcogenide Ca2O3Fe2.6S2 that contains both planar [Ca2FeO2](2+) and [Fe2OS2](2-) layers with the shortest Fe-Fe bond length. This compound is a narrow band gap (~0.073 eV) Mott insulator. The observed antiferromagnetic (AFM) transition at 77 K is due to the ordered Fe vacancies, which can be suppressed by partial substitution of Se for S. We show that the vacancy-free phase Ca2O3Fe3S2 may become a metal with moderate electron correlation comparable to the parent compound LaOFeAs of corresponding superconductors. Our results imply that iron oxychalcogenide can be converted from an AFM Mott insulator into a bad metal like iron pnictides through Fe-Fe bond length shrinking.
authors.affiliation: Research & Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiaozhi
authors.initials: X
authors.lastname: Wu
authors.forename: Dandan
authors.initials: D
authors.lastname: Li
authors.forename: Shifeng
authors.initials: S
authors.lastname: Jin
authors.forename: Xiao
authors.initials: X
authors.lastname: Chen
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Lin
authors.forename: Shijie
authors.initials: S
authors.lastname: Shen
authors.forename: Duanduan
authors.initials: D
authors.lastname: Yuan
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Chen