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Orbital Selective Spin Excitations and their Impact on Superconductivity of LiFe 1 − x Co x As

2016; American Physical Society; Volume: 116; Issue: 24 Linguagem: Inglês

10.1103/physrevlett.116.247001

1092-0145

Li Yu, Zhiping Yin, Xiancheng Wang, David W. Tam, D. L. Abernathy, A. Podlesnyak, Chenglin Zhang, Meng Wang, Lingyi Xing, Changqing Jin, Kristjan Haule, Gabriel Kotliar, Thomas Maier, Pengcheng Dai,

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We use neutron scattering to study spin excitations in single crystals of LiFe_{0.88}Co_{0.12}As, which is located near the boundary of the superconducting phase of LiFe_{1-x}Co_{x}As and exhibits non-Fermi-liquid behavior indicative of a quantum critical point. By comparing spin excitations of LiFe_{0.88}Co_{0.12}As with a combined density functional theory and dynamical mean field theory calculation, we conclude that wave-vector correlated low energy spin excitations are mostly from the d_{xy} orbitals, while high-energy spin excitations arise from the d_{yz} and d_{xz} orbitals. Unlike most iron pnictides, the strong orbital selective spin excitations in the LiFeAs family cannot be described by an anisotropic Heisenberg Hamiltonian. While the evolution of low-energy spin excitations of LiFe_{1-x}Co_{x}As is consistent with the electron-hole Fermi surface nesting conditions for the d_{xy} orbital, the reduced superconductivity in LiFe_{0.88}Co_{0.12}As suggests that Fermi surface nesting conditions for the d_{yz} and d_{xz} orbitals are also important for superconductivity in iron pnictides.