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arXiv · 1511.04267

Spin nematic susceptibility studied by inelastic neutron scattering in FeSe

S. Shamoto·K. Matsuoka·R. Kajimoto·M. Ishikado·Y. Yamakawa·T. Watashige·S. Kasahara·M. Nakamura·H. Kontani·T. Shibauchi·Y. Matsuda
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Abstract

Mechanism of unconventional superconductivity in FeSe has been intensely scrutinized recently because of a variety of exotic properties unprecedented for other iron-based superconductors. A central unanswered question concerns the origin of the interaction that causes the nematic transition at $T_s=90\,K$ without accompanying magnetic order. Elucidating the nature of spin excitations in the normal state is a key to addressing this issue. Here we report, from inelastic neutron-scattering measurements in FeSe single crystals, that high-energy spin excitation spectra of FeSe exhibit characteristic energy dependence with missing intensity at around 70-80$\,$meV, which are very different from other iron-based superconductors. Despite of the strongest electron correlations among the iron-based superconductor family, the spectra are qualitatively at variance with the local moment model and can be essentially described by the itinerant electron picture. Moreover, the dynamical spin susceptibility above $T_s$ is only weakly temperature dependent, which is in stark contrast to the Curie-Weiss behavior of the electronic nematic susceptibility, suggesting that the nematic transition is not likely driven by spin but by orbital degrees of freedom.

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S. Shamoto, K. Matsuoka, R. Kajimoto, M. Ishikado, Y. Yamakawa, T. Watashige, S. Kasahara, M. Nakamura, H. Kontani, T. Shibauchi, Y. Matsuda. 2016-09-22. Spin nematic susceptibility studied by inelastic neutron scattering in FeSe. https://arxiv.org/abs/1511.04267

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