Preferred spin excitations in the bilayer iron-based superconductor CaK ( Fe$_{0.96}$Ni$_{0.04}$)$_4$As$_4$ with spin-vortex crystal order - Archive ouverte HAL
Article Dans Une Revue Physical Review Letters Année : 2022

Preferred spin excitations in the bilayer iron-based superconductor CaK ( Fe$_{0.96}$Ni$_{0.04}$)$_4$As$_4$ with spin-vortex crystal order

Chang Liu
Tao Xie
Haranath Ghosh
Soumyadeep Ghosh
Xiaoyan Ma
  • Fonction : Auteur
Shiliang Li
  • Fonction : Auteur
Yuan Li
Huiqian Luo

Résumé

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 CaK Fe$_{0.96}$Ni$_{0.04}$$_4$As$_4$ 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 L symmetries due to the bilayer coupling are found similar to the undoped compound CaKFe$_4$As$_4$ but at lower energies. Polarization analysis reveals that the odd mode is c-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 c-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 c-axis preferred magnetic excitations below Tc regardless of the details of magnetic pattern or lattice symmetry.
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Dates et versions

hal-03794953 , version 1 (03-10-2022)

Identifiants

Citer

Chang Liu, Philippe Bourges, Yvan Sidis, Tao Xie, Guanghong He, et al.. Preferred spin excitations in the bilayer iron-based superconductor CaK ( Fe$_{0.96}$Ni$_{0.04}$)$_4$As$_4$ with spin-vortex crystal order. Physical Review Letters, 2022, 128 (13), pp.137003. ⟨10.1103/PhysRevLett.128.137003⟩. ⟨hal-03794953⟩
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