Normal-State Hourglass Dispersion of the Spin Excitations inFeSexTe1−x

Shiliang Li, Chenglin Zhang, Meng Wang, Hui-qian Luo, Xingye Lu, Enrico Faulhaber, Astrid Schneidewind, Peter Link, Jiangping Hu, Tao Xiang, Pengcheng Dai
2010 Physical Review Letters  
We use cold neutron spectroscopy to study the low-energy spin excitations of superconducting (SC) FeSe_0.4Te_0.6 and essentially non-superconducting (NSC) FeSe_0.45Te_0.55. In contrast to BaFe_2-x(Co,Ni)_xAs_2, where the low-energy spin excitations are commensurate both in the SC and normal state, the normal-state spin excitations in SC FeSe_0.4Te_0.6 are incommensurate and show an hourglass dispersion near the resonance energy. Since similar hourglass dispersion is also found in the NSC
more » ... 45Te_0.55, we argue that the observed incommensurate spin excitations in FeSe_1-xTe_x are not directly associated with superconductivity. Instead, the results can be understood within a picture of Fermi surface nesting assuming extremely low Fermi velocities and spin-orbital coupling.
doi:10.1103/physrevlett.105.157002 pmid:21230929 fatcat:77wv665fqjgzbokacy4hg5nmcm