Ferromagnetic inter-layer coupling in FeSe$_{1-x}$S$_{x}$ superconductors revealed by inelastic neutron scattering

Mingwei Ma; Philippe Bourges; Yvan Sidis; Jinzhao Sun; Guoqing Wang; Kazuki Iida; Kazuya Kamazawa; Jitae T. Park; Frederic Bourdarot; Zhian Ren; Yuan Li

doi:10.1103/physrevb.110.174503

arXiv · 2407.05548

Ferromagnetic inter-layer coupling in FeSe$_{1-x}$S$_{x}$ superconductors revealed by inelastic neutron scattering

Mingwei Ma·Philippe Bourges·Yvan Sidis·Jinzhao Sun·Guoqing Wang·Kazuki Iida·Kazuya Kamazawa·Jitae T. Park·Frederic Bourdarot·Zhian Ren·Yuan Li

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Abstract

FeSe$_{1-x}$S$_{x}$ superconductors are commonly considered layered van der Waals materials with negligible inter-layer coupling. Here, using inelastic neutron scattering to study spin excitations in single-crystal samples, we reveal that the magnetic coupling between adjacent Fe layers is not only significant, as it affects excitations up to \textcolor{black}{15} meV, but also ferromagnetic in nature, making the system different from most unconventional superconductors including iron pnictides. Our observation provides a new standpoint to understand the absence of magnetic order in FeSe$_{1-x}$S$_{x}$. Since intercalating between the Fe layers is known to enhance superconductivity and suppress the inter-layer coupling, superconductivity appears to be a more robust phenomenon in the two-dimensional limit than antiferromagnetic order.

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Mingwei Ma, Philippe Bourges, Yvan Sidis, Jinzhao Sun, Guoqing Wang, Kazuki Iida, Kazuya Kamazawa, Jitae T. Park, Frederic Bourdarot, Zhian Ren, Yuan Li. 2024-07-08. Ferromagnetic inter-layer coupling in FeSe$_{1-x}$S$_{x}$ superconductors revealed by inelastic neutron scattering. https://doi.org/10.1103/physrevb.110.174503

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