title: Normal-state hourglass dispersion of the spin excitations in FeSexTe(1-x).
abstract: We use cold neutron spectroscopy to study the low-energy spin excitations of superconducting (SC) FeSe0.4Te0.6 and essentially nonsuperconducting (NSC) FeSe0.45Te0.55. In contrast with BaFe2-x(Co,Ni)xAs2, where the low-energy spin excitations are commensurate both in the SC and normal state, the normal-state spin excitations in SC FeSe0.4Te0.6 are incommensurate and show an hourglass dispersion near the resonance energy. Since similar hourglass dispersion is also found in the NSC FeSe0.45Te0.55, we argue that the observed incommensurate spin excitations in FeSe(1-x)Tex are not directly associated with superconductivity. Instead, the results can be understood within a picture of Fermi surface nesting assuming extremely low Fermi velocities and spin-orbital coupling.
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Shiliang
authors.initials: S
authors.lastname: Li
authors.forename: Chenglin
authors.initials: C
authors.lastname: Zhang
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.forename: Hui-Qian
authors.initials: HQ
authors.lastname: Luo
authors.forename: Xingye
authors.initials: X
authors.lastname: Lu
authors.forename: Enrico
authors.initials: E
authors.lastname: Faulhaber
authors.forename: Astrid
authors.initials: A
authors.lastname: Schneidewind
authors.forename: Peter
authors.initials: P
authors.lastname: Link
authors.forename: Jiangping
authors.initials: J
authors.lastname: Hu
authors.forename: Tao
authors.initials: T
authors.lastname: Xiang
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Dai