论文标题
基于二维铁的超导体中的中子自旋共振
Neutron spin resonance in a quasi-two-dimensional iron-based superconductor
论文作者
论文摘要
磁性介导的库珀配对通常被视为建立非常规超导性的统一机制的关键。一个关键的证据是在超导状态下产生的中子自旋共振，通常将其解释为限制在超导成对的隔离间隙（$2Δ$）下方的集体颗粒孔激发中的自旋效果。 Here, on the basis of inelastic neutron scattering measurements on a quasi-two-dimensional iron-based superconductor KCa$_2$Fe$_4$As$_4$F$_2$, we have discovered a two-dimensional spin resonant mode with downward dispersions, a behavior closely resembling the low branch of the hour-glass-type spin resonance in cuprates.谐振强度占主导地位，两个广泛的不相称的峰接近$ q = $ = $（0.5，0.5），$ e_r = 16 $ meV的尖峰峰值。模式的总体能量分散超过测量的最大总间隙$δ_ {\ rm tot} = |δ_k|+|+|δ_{k+q} | $。这些实验结果深深地挑战了对谐振模式的常规理解，无论强调配对对称方案如何，它也指出，当基于铁的基于铁的超导性变得非常准二维时，电子行为与杯形相似。
Magnetically mediated Cooper pairing is generally regarded as a key to establish the unified mechanism of unconventional superconductivity. One crucial evidence is the neutron spin resonance arising in the superconducting state, which is commonly interpreted as a spin-exciton from collective particle-hole excitations confined below the superconducting pair-breaking gap ($2Δ$). Here, on the basis of inelastic neutron scattering measurements on a quasi-two-dimensional iron-based superconductor KCa$_2$Fe$_4$As$_4$F$_2$, we have discovered a two-dimensional spin resonant mode with downward dispersions, a behavior closely resembling the low branch of the hour-glass-type spin resonance in cuprates. The resonant intensity is predominant by two broad incommensurate peaks near $Q=$(0.5, 0.5) with a sharp energy peak at $E_R=16$ meV. The overall energy dispersion of the mode exceeds the measured maximum total gap $Δ_{\rm tot}=|Δ_k|+|Δ_{k+Q}|$. These experimental results deeply challenge the conventional understanding of the resonance modes as magnetic excitons regardless of underlining pairing symmetry schemes, and it also points out that when the iron-based superconductivity becomes very quasi-two-dimensional, the electronic behaviors are similar to those in cuprates.
