We report neutron inelastic scattering measurements on the normal and superconducting states of single-crystalline Cs0.8Fe1.9Se2. Consistent with previous measurements on Rb(x)Fe(2-y)Se2, we observe two distinct spin excitation signals: (i) spin-wave excitations characteristic of the block antiferromagnetic order found in insulating A(x)Fe(2-y)Se2 compounds, and (ii) a resonance-like magnetic peak localized in energy at 11 meV and at an in-plane wave vector of (0.25, 0.5). The resonance peak increases below Tc = 27 K, and has a similar absolute intensity to the resonance peaks observed in other Fe-based superconductors. The existence of a magnetic resonance in the spectrum of Rb(x)Fe(2-y)Se2 and now of Cs(x)Fe(2-y)Se2 suggests that this is a common feature of superconductivity in this family. The low energy spin-wave excitations in Cs0.8Fe1.9Se2 show no measurable response to superconductivity, consistent with the notion of spatially separate magnetic and superconducting phases.
@article{arxiv.1208.3610,
title = {Spin-wave excitations and superconducting resonant mode in Cs(x)Fe(2-y)Se2},
author = {A. E. Taylor and R. A. Ewings and T. G. Perring and J. S. White and P. Babkevich and A. Krzton-Maziopa and E. Pomjakushina and K. Conder and A. T. Boothroyd},
journal= {arXiv preprint arXiv:1208.3610},
year = {2012}
}
Comments
7 pages, 5 figures. v2 corrects a misquoted numerical value in text