Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc su-perconductors.In iron-based superconductors,spin excitations at low energy range,especially the spin-resonance mode at ER～5kBTc,are important for understanding the superconductivity.Here,we use inelastic neutron scattering(INS)to investigate the symmetry and in-plane wave-vector dependence of low-energy spin excitations in uniaxial-strain detwinned FeSe.The low-energy spin excitations(E＜10meV)appear mainly at Q=(±1,0)in the superconducting state(T(＜)9K)and the nematic state(T(＜)90 K),confirming the constant C2 rotational symmetry and ruling out the C4 mode at E ≈ 3 meV reported in a prior INS study.Moreover,our results reveal an isotropic spin resonance in the superconducting state,which is consistent with the s±wave pairing symmetry.At slightly higher energy,low-energy spin excitations become highly anisotropic.The full width at half maximum of spin excitations is elongated along the transverse direction.The Q-space isotropic spin resonance and highly anisotropic low-energy spin excitations could arise from dyz intra-orbital selective Fermi surface nesting between the hole pocket around Γ point and the electron pockets centered at Mx point.
刘瑞鲜、Mitsutaka Nakamura、Kazuya Kamazawa、鲁兴业
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Center for Advanced Quantum Studies,School of Physics and Astronomy,Beijing Normal University,Beijing 100875,China
J-PARC Center,Japan Atomic Energy Agency(JAEA),Tokai,Ibaraki 319-1195,Japan
Research Center for Neutron Science and Technology,Comprehensive Research Organization for Science and Society,Tokai,Ibaraki 319-1106,Japan
Fundamental Research Funds for the Central UniversitiesNational Key Projects for Research and Development of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of Chinaneutron beamtimes from J-PARC
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