title: Doping dependence of spin excitations and its correlations with high-temperature superconductivity in iron pnictides.
abstract: High-temperature superconductivity in iron pnictides occurs when electrons and holes are doped into their antiferromagnetic parent compounds. Since spin excitations may be responsible for electron pairing and superconductivity, it is important to determine their electron/hole-doping evolution and connection with superconductivity. Here we use inelastic neutron scattering to show that while electron doping to the antiferromagnetic BaFe₂As₂ parent compound modifies the low-energy spin excitations and their correlation with superconductivity (<50 meV) without affecting the high-energy spin excitations (>100 meV), hole-doping suppresses the high-energy spin excitations and shifts the magnetic spectral weight to low-energies. In addition, our absolute spin susceptibility measurements for the optimally hole-doped iron pnictide reveal that the change in magnetic exchange energy below and above T(c) can account for the superconducting condensation energy. These results suggest that high-T(c) superconductivity in iron pnictides is associated with both the presence of high-energy spin excitations and a coupling between low-energy spin excitations and itinerant electrons.
authors.affiliation: 1] Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China [2].
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.forename: Chenglin
authors.initials: C
authors.lastname: Zhang
authors.forename: Xingye
authors.initials: X
authors.lastname: Lu
authors.forename: Guotai
authors.initials: G
authors.lastname: Tan
authors.forename: Huiqian
authors.initials: H
authors.lastname: Luo
authors.forename: Yu
authors.initials: Y
authors.lastname: Song
authors.forename: Miaoyin
authors.initials: M
authors.lastname: Wang
authors.forename: Xiaotian
authors.initials: X
authors.lastname: Zhang
authors.forename: E A
authors.initials: EA
authors.lastname: Goremychkin
authors.forename: T G
authors.initials: TG
authors.lastname: Perring
authors.forename: T A
authors.initials: TA
authors.lastname: Maier
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Yin
authors.forename: Kristjan
authors.initials: K
authors.lastname: Haule
authors.forename: Gabriel
authors.initials: G
authors.lastname: Kotliar
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Dai