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arXiv · 1803.00779

Neutron spin resonance in the 112-type iron-based superconductor

Tao Xie·Dongliang Gong·Haranath Ghosh·Abyay Ghosh·Minoru Soda·Takatsugu Masuda·Shinichi Itoh·Frederic Bourdarot·Louis-Pierre Regnault·Sergey Danilkin·Shiliang Li·Huiqian Luo
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Abstract

We use inelastic neutron scattering to study the low-energy spin excitations of 112-type iron pnictide Ca$_{0.82}$La$_{0.18}$Fe$_{0.96}$Ni$_{0.04}$As$_{2}$ with bulk superconductivity below $T_c=22$ K. A two-dimensional spin resonance mode is found around $E=$ 11 meV, where the resonance energy is almost temperature independent and linearly scales with $T_c$ along with other iron-based superconductors. Polarized neutron analysis reveals the resonance is nearly isotropic in spin space without any $L$ modulations. Due to the unique monoclinic structure with additional zigzag arsenic chains, the As $4p$ orbitals contribute to a three-dimensional hole pocket around $\Gamma$ point and an extra electron pocket at $X$ point. Our results suggest that the energy and momentum distribution of spin resonance does not directly response to the $k_z$ dependence of fermiology, and the spin resonance intrinsically is a spin-1 mode from singlet-triplet excitations of the Cooper pairs in the case of weak spin-orbital coupling.

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Tao Xie, Dongliang Gong, Haranath Ghosh, Abyay Ghosh, Minoru Soda, Takatsugu Masuda, Shinichi Itoh, Frederic Bourdarot, Louis-Pierre Regnault, Sergey Danilkin, Shiliang Li, Huiqian Luo. 2018-03-02. Neutron spin resonance in the 112-type iron-based superconductor. https://doi.org/10.1103/physrevlett.120.137001

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