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Preferred Magnetic Excitations in the Iron-Based Sr_{1-x}Na_{x}Fe_{2}As_{2} Superconductor
Jianqing Guo1, Li Yue1, Kazuki Iida2
1International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
Abstract:
With spin-orbit coupling, both local-moment magnetism and itinerant electrons are expected to behave anisotropically in spin space, but such effects' influence on the formation of unconventional superconductivity has been hitherto unexplored. Here, in an iron-based superconductor, Sr_{1-x}Na_{x}Fe_{2}As_{2}, we report spectroscopic evidence that itinerant electrons "prefer" to be assisted by c-axis polarized magnetic excitations in their formation of superconducting Cooper pairs, against the polarization of the local-moment excitations. Our result naturally explains why the superconductivity competes strongly with the tetragonal magnetic phase in this material, and provides a fresh view on how to make a good superconductor out of a magnetic "Hund's metal."
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