title: Development of a ferromagnetic component in the superconducting state of Fe-excess Fe1.12Te(1-x)Sex by electronic charge redistribution.
abstract: The general picture established so far for the links between superconductivity and magnetic ordering in iron chalcogenide Fe1+y(Te(1-x)Sex) is that the substitution of Se for Te directly drives the system from the antiferromagnetic end into the superconducting regime. Here, we report on the observation of a ferromagnetic component that developed together with the superconducting transition in Fe-excess Fe1.12Te(1-x)Sex crystals using neutron and x-ray diffractions, resistivity, magnetic susceptibility and magnetization measurements. The superconducting transition is accompanied by a negative thermal expansion of the crystalline unit cell and an electronic charge redistribution, where a small portion of the electronic charge flows from around the Fe sites toward the Te/Se sites. First-principles calculations show consistent results, revealing that the excess Fe ions play a more significant role in affecting the magnetic property in the superconducting state than in the normal state and the occurrence of an electronic charge redistribution through the superconducting transition.
authors.affiliation: Department of Physics, National Central University, Jhongli 32001, Taiwan.
authors.forename: Wen-Hsien
authors.initials: WH
authors.lastname: Li
authors.affiliation: Department of Physics, National Central University, Jhongli 32001, Taiwan.
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Karna
authors.affiliation: Department of Physics, National Central University, Jhongli 32001, Taiwan.
authors.forename: Han
authors.initials: H
authors.lastname: Hsu
authors.affiliation: Department of Physics, National Central University, Jhongli 32001, Taiwan.
authors.forename: Chi-Yen
authors.initials: CY
authors.lastname: Li
authors.affiliation: Department of Physics, National Central University, Jhongli 32001, Taiwan.
authors.forename: Chi-Hung
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Raman
authors.initials: R
authors.lastname: Sankar
authors.affiliation: Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Fang Cheng
authors.initials: FC
authors.lastname: Chou