Abstract
Spin-orbit coupling (SOC) is a key to understand the magnetically driven superconductivity in iron-based superconductors, where both local and itinerant electrons are present and the orbital angular momentum is not completely quenched. Here, we report a neutron scattering study on the bilayer compound with superconductivity coexisting with a noncollinear spin-vortex crystal magnetic order that preserves the tetragonal symmetry of the Fe-Fe plane. In the superconducting state, two spin resonance modes with odd and even symmetries due to the bilayer coupling are found similar to the undoped compound but at lower energies. Polarization analysis reveals that the odd mode is -axis polarized, and the low-energy spin anisotropy can persist to the paramagnetic phase at high temperature, which closely resembles other systems with in-plane collinear and -axis biaxial magnetic orders. These results provide the missing piece of the puzzle on the SOC effect in iron-pnictide superconductors, and also establish a common picture of -axis preferred magnetic excitations below regardless of the details of magnetic pattern or lattice symmetry.
- Received 10 January 2022
- Accepted 23 February 2022
DOI:https://doi.org/10.1103/PhysRevLett.128.137003
© 2022 American Physical Society
Physics Subject Headings (PhySH)
synopsis
Spin Fluctuations May Drive Iron-Based Superconductivity
Published 31 March 2022
An experiment finds that spin fluctuations in an iron-based superconductor have a preferred direction, suggesting a potential mechanism for superconductivity in these materials.
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