Abstract
We use neutron scattering to study spin excitations in single crystals of , which is located near the boundary of the superconducting phase of and exhibits non-Fermi-liquid behavior indicative of a quantum critical point. By comparing spin excitations of 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 orbitals, while high-energy spin excitations arise from the and 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 is consistent with the electron-hole Fermi surface nesting conditions for the orbital, the reduced superconductivity in suggests that Fermi surface nesting conditions for the and orbitals are also important for superconductivity in iron pnictides.
- Received 18 January 2016
DOI:https://doi.org/10.1103/PhysRevLett.116.247001
© 2016 American Physical Society