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arXiv · 0902.0813

Spin gap and magnetic resonance in superconducting BaFe$_{1.9}$Ni$%_{0.1}$As$_{2}$

Shiliang Li·Ying Chen·Sung Chang·Jeffrey W. Lynn·Linjun Li·Yongkang Luo·Guanghan Cao·Zhu'an Xu·Pengcheng Dai
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Abstract

We use neutron spectroscopy to determine the nature of the magnetic excitations in superconducting BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$ ($T_{c}=20$ K). Above $T_{c}$ the excitations are gapless and centered at the commensurate antiferromagnetic wave vector of the parent compound, while the intensity exhibits a sinusoidal modulation along the c-axis. As the superconducting state is entered a spin gap gradually opens, whose magnitude tracks the $T$-dependence of the superconducting gap observed by angle resolved photoemission. Both the spin gap and magnetic resonance energies are temperature \textit{and} wave vector dependent, but their ratio is the same within uncertainties. These results suggest that the spin resonance is a singlet-triplet excitation related to electron pairing and superconductivity.

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Shiliang Li, Ying Chen, Sung Chang, Jeffrey W. Lynn, Linjun Li, Yongkang Luo, Guanghan Cao, Zhu'an Xu, Pengcheng Dai. 2009-02-04. Spin gap and magnetic resonance in superconducting BaFe$_{1.9}$Ni$%_{0.1}$As$_{2}$. https://doi.org/10.1103/physrevb.79.174527

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