Quasi-one-dimensional $A_2{\mathrm{Cr}}_3{\mathrm{As}}_3$ (with $A=\text{K}$, Cs, Rb) is an intriguing new family of superconductors which exhibit many similar features to the cuprate and iron-based unconventional superconductor families. Yet, in contrast to these systems, no charge or magnetic ordering has been observed which could provide the electronic correlations presumed necessary for an unconventional superconducting pairing mechanism—an absence which defies predictions of first-principles models. We report the results of neutron scattering experiments on polycrystalline ${\mathrm{K}}_2{\mathrm{Cr}}_3{\mathrm{As}}_3$ ($T_c\sim 7\text{K}$) which probed the low-temperature dynamics near $T_c$. Neutron diffraction data evidence a subtle response of the nuclear lattice to the onset of superconductivity while inelastic scattering reveals a highly dispersive column of intensity at the commensurate wave vector $q=\left(00\frac{1}{2}\right)$ which loses intensity beneath $T_c$—indicative of short-range magnetic fluctuations. Using linear spin-wave theory, we model the observed scattering and suggest a possible structure to the short-range magnetic order. These observations suggest that ${\mathrm{K}}_2{\mathrm{Cr}}_3{\mathrm{As}}_3$ is in close proximity to a magnetic instability and that the incipient magnetic order both couples strongly to the lattice and competes with superconductivity, in direct analogy with the iron-based superconductors.

中文翻译：

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准一维K2Cr3As3中结构与磁和超导阶的耦合

准一维 ${\mathrm{一个}}_{\mathrm{2个}}{铬}_3{\mathrm{作为}}_3$ （和 $\mathrm{一个}=\text{ķ}$（Cs，Rb）是一个令人着迷的新超导体系列，与铜酸盐和铁基非常规超导体系列具有许多相似的功能。但是，与这些系统相比，没有观察到电荷或磁排序可以提供非常规超导配对机制所必需的电子相关性，而这种缺失不符合第一性原理模型的预测。我们报告了多晶上中子散射实验的结果${\mathrm{ķ}}_{\mathrm{2个}}{铬}_3{\mathrm{作为}}_3$ （${Ť}_C〜7\text{ķ}$）探讨了附近的低温动力学 ${Ť}_C$。中子衍射数据证明了核晶格对超导性的微妙响应，而无弹性散射则在相应的波矢处显示出高度分散的强度列$q=\left(00\frac{\mathrm{1个}}{\mathrm{2个}}\right)$ 在下面失去强度 ${Ť}_C$-表示短程电磁波动。使用线性自旋波理论，我们对观察到的散射进行建模，并为短程磁阶建议了一种可能的结构。这些观察表明${\mathrm{ķ}}_{\mathrm{2个}}{铬}_3{\mathrm{作为}}_3$ 与铁基超导体非常相似，它与磁性不稳定性非常接近，并且初始磁性顺序既牢固地耦合到晶格，又与超导电性竞争。