Song, YuLu, XingyeAbernathy, D.L.Tam, David W.Niedziela, J.L.Tian, WeiLuo, HuiqianSi, QimiaoDai, Pengcheng2016-01-152016-01-152015Song, Yu, Lu, Xingye, Abernathy, D.L., et al.. "Energy dependence of the spin excitation anisotropy in uniaxial-strained BaFe1.9Ni0.1As2." <i>Physical Review B,</i> 92, no. 18 (2015) American Physical Society: 180504(R). http://dx.doi.org/10.1103/PhysRevB.92.180504.https://hdl.handle.net/1911/87852We use inelastic neutron scattering to study the temperature and energy dependence of the spin excitation anisotropy in uniaxial-strained electron-doped iron pnictide BaFe1.9Ni0.1As2 near optimal superconductivity (Tc=20K). Our work has been motivated by the observation of in-plane resistivity anisotropy in the paramagnetic tetragonal phase of electron-underdoped iron pnictides under uniaxial pressure, which has been attributed to a spin-driven Ising-nematic state or orbital ordering. Here we show that the spin excitation anisotropy, a signature of the spin-driven Ising-nematic phase, exists for energies below ∼60 meV in uniaxial-strained BaFe1.9Ni0.1As2. Since this energy scale is considerably larger than the energy splitting of the dxz and dyz bands of uniaxial-strained Ba(Fe1−xCox)2As2 near optimal superconductivity, spin Ising-nematic correlations are likely the driving force for the resistivity anisotropy and associated electronic nematic correlations.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articlehttp://dx.doi.org/10.1103/PhysRevB.92.180504