FeSe1−𝑥⁢S𝑥 superconductors are commonly considered layered van der Waals materials with negligible interlayer 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 ferromagnetic in nature, making the system different from most unconventional superconductors including iron pnictides. The weak interlayer coupling is estimated to be 𝐽𝑐∼ 0.2 meV, in agreement with the short spin-spin correlation length 𝜉𝑐∼0.2⁢𝑐 along the 𝑐 axis. The results provide an experimental basis for establishing a microscopic theoretical model to describe the absence of magnetic order in FeSe1−𝑥⁢S𝑥.

中文翻译：

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非弹性中子散射揭示的铁磁层间耦合 inFeSe1−xSx超导体


FeSe1−xSx 超导体通常被认为是层状范德华材料，层间耦合可以忽略不计。在这里，使用非弹性中子散射来研究单晶样品中的自旋激发，我们揭示了相邻 Fe 层之间的磁耦合本质上是铁磁性的，这使得该系统不同于包括铁镍钛合金在内的大多数非常规超导体。弱层间耦合估计为 Jc∼ 0.2 meV，与沿 c 轴的短自旋-自旋相关长度 ξc∼0.2c 一致。结果为建立微观理论模型来描述 FeSe1−xSx 中不存在磁有序性提供了实验依据。