title: Magnetic ground state of FeSe.
abstract: Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities.
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Qisi
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Bingying
authors.initials: B
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Research Center for Neutron Science and Technology, Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ikeuchi
authors.affiliation: Research Center for Neutron Science and Technology, Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Iida
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Christianson
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot OX11 0QX, United Kingdom.
authors.forename: H C
authors.initials: HC
authors.lastname: Walker
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot OX11 0QX, United Kingdom.
authors.forename: D T
authors.initials: DT
authors.lastname: Adroja
authors.affiliation: Center for High Pressure Science and Technology Advanced Research, Shanghai, 201203, China.|Faculty of Science, Department of Physics, Fayoum University, 63514 Fayoum, Egypt.
authors.forename: M
authors.initials: M
authors.lastname: Abdel-Hafiez
authors.affiliation: Center for High Pressure Science and Technology Advanced Research, Shanghai, 201203, China.
authors.forename: Xiaojia
authors.initials: X
authors.lastname: Chen
authors.affiliation: Institute of Experimental Mineralogy, Russian Academy of Sciences, 142432 Chernogolovka, Russia.|Institute of Physics and Technology, Ural Federal University, 620002 Ekaterinburg, Russia.
authors.forename: D A
authors.initials: DA
authors.lastname: Chareev
authors.affiliation: Institute of Physics and Technology, Ural Federal University, 620002 Ekaterinburg, Russia.|Low Temperature Physics and Superconductivity Department, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia.|National University of Science and Technology 'MISiS', Moscow 119049, Russia.
authors.forename: A N
authors.initials: AN
authors.lastname: Vasiliev
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
authors.forename: Jun
authors.identifier: 0000-0002-0421-8934
authors.initials: J
authors.lastname: Zhao