Orbital selective spin excitations and their impact on superconductivity of LiFe1-xCoxAs

• Published in: arXiv.org 2016-06
• Main Authors: Li, Yu, Yin, Zhiping, Wang, Xiancheng, Tam, David W, Abernathy, D L, Podlesnyak, A, Zhang, Chenglin, Wang, Meng, Xing, Lingyi, Jin, Changqing, Haule, Kristjan, Kotliar, Gabriel, Maier, Thomas A, Dai, Pengcheng
• Format: Article
• Language: English
• Subjects: Critical point; Density functional theory; Excitation; Fermi surfaces; Group 5A compounds; Holes (electron deficiencies); Iron; Mean field theory; Nesting; Neutron scattering; Neutrons; Orbitals; Single crystals; Superconductivity; Superconductors
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1606.00727

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 (DFT) and dynamical mean field theory (DMFT) 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 LiFeAs family cannot be described by anisotropic Heisenberg Hamiltonian. While the evolution of low-energy spin excitations of LiFe\(_{1-x}\)Co\(_x\)As are consistent with electron-hole Fermi surface nesting condition 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.