铁硒化合物Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$单晶的光学性质
Optical Properties of Iron-Selenide Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$ Single Crystals
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中文总结 AI 辅助
研究超导Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$单晶光学性质，用德鲁德 - 洛伦兹模型分析正常态响应，给出相关温度依赖性，发现特定模式，揭示该化合物中超导与磁性介观共存。
中文摘要 AI 辅助
利用红外傅里叶变换光谱和光谱椭偏仪，我们在4 - 300K温度范围内，对临界温度$T_c\approx 34.3$K的超导Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$单晶的面内反射率进行了广泛频率范围的研究。通过含一个德鲁德分量的德鲁德 - 洛伦兹模型分析了其正常态响应，给出了正常态下德鲁德分量的等离子体频率、光导率、散射率和直流电阻率的温度依赖性。报告了在1430~cm$^{-1}$处的法诺形状模式，表明离散模式（可能与某些电子跃迁有关）与双磁振子连续体的耦合，以及低频宽带（归因于反铁磁超结构的声学磁振子分支）。这些特征在正常态和超导态的反射率中均存在，表明Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$中存在超导和磁性的介观共存。
英文摘要
With infrared Fourier-transform spectroscopy and spectroscopic ellipsometry we investigated the in-plane reflectance of the superconducting Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$ single crystals with a critical temperature $T_c\approx 34.3$ K over a broad frequency range at temperatures of 4--300 K. The normal-state response of Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$ is analyzed by a Drude-Lorentz model with one Drude component. The temperature dependences of the plasma frequency, optical conductivity, scattering rate, and dc resistivity of the Drude component in the normal state are presented. We report a Fano-shaped mode at 1430~cm$^{-1}$ indicating a coupling of the discrete mode presumably related to some electronic transition to a two-magnon continuum as well as a low-frequency broad band assigned to the acoustic magnon branch of the antiferromagnetic superstructure. These features persist in the reflectance in both the normal and superconducting states suggesting a mesoscopic coexistence of superconductivity and magnetism in Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$.
