标题： 前形成的库珀对在三斜铁砷化物超导体中 显示英文标题

标题： Preformed Cooper Pairs in a Triclinic Iron Pnictide Superconductor

摘要： 电子配对与相位相干在临界温度以下产生超导性 ($T_c$)。 在掺杂不足的高温$T_c$陶瓷中，这两种量子现象可能在不同的温度下发生，这最近在准二维 (准-2D) 铁硫化物超导体中得到了证实。 这里，我们报告了对三斜铁砷化物超导体 (Ca$_{0.85}$La$_{0.15}$)$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$在$T_c \approx $30 K 下的预配对行为的系统研究，其中超导性表现为准二维性，由贝雷津-科斯特里茨-索利斯行为所体现。 非弹性中子散射实验明确揭示了超导态中约$E_R =$13 meV 处的自旋共振峰，但其强度在升温穿过$T_c$时持续减弱，并伴随自旋关联在$T^{*}\approx$45 K 附近出现异常，且平面内磁场的抑制作用持续到相同温度。 低于$T^{*}$时，也观察到了显著的Nernst信号和费米能级态密度的降低。 这些结果表明，自旋共振的前驱体与由相位涨落驱动的预先形成的库珀对高度相关，类似于铜氧化物中的赝能隙情况。 显示英文摘要

摘要： Electron pairing along with phase coherence generates superconductivity below the critical temperature ($T_c$). In underdoped high-$T_c$ cuprates, these two quantum phenomena may occur at separate temperatures, which was lately confirmed in the quasi-two-dimensional (quasi-2D) iron chalcogenide superconductors. Here, we report a systematic investigation on the pre-pairing behavior in a triclinic iron pnictide superconductor (Ca$_{0.85}$La$_{0.15}$)$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$ with $T_c \approx $ 30 K, where the superconductivity is quasi-2D manifested by the Berezinskii-Kosterlitz-Thouless behaviors. Inelastic neutron scattering experiments unambiguously reveal a spin resonance peak around $E_R =$ 13 meV in the superconducting state, but its intensity continuously decreases when warming up across $T_c$, accompanied with an anomaly around $T^{*}\approx$ 45 K in spin correlations, and a suppression by an in-plane magnetic field persisting to the same temperature. Below $T^{*}$, a significant Nernst signal and a reduction of density of states at the Fermi level are also observed. These results suggest that the precursor of spin resonance is highly related to the preformed Cooper pairs driven by phase fluctuations, much like the pseudogap case in cuprates.