铁基超导体Li0.8Fe0.2ODFeSe的红外光谱研究

测量和研究了铁基超导体Li_0.8Fe_0.2ODFeSe单晶的红外光学响应，发现室温下光电导率谱不存在Drude分量，载流子具有非相干输运行为.随着温度降低，Drude分量形成并不断变窄，同时在相应的反射率谱上出现清晰的等离子体边，表明散射率急剧降低.在最低温度，观察到超导能隙形成导致的光谱变化，光电导率谱在160 cm^-1以下受到显著压制.对比FeSe单晶的光谱数据，发现整体的光电导率谱型很相似，但自由载流子的谱重更低，揭示出样品具有更低的载流子浓度.另外还观察到温度变化诱导的谱重由低频向高频区域转移的现象，表明其存在强关联效应.

Infrared spectroscopy study of ironbased superconductor Li0.8Fe0.2 ODFeSe

We perform an in-plane optical spectroscopy measurement on iron-based superconductor Li_0.8Fe_0.2ODFeSe single crystal. At room temperature, the low frequency optical conductivity shows an incoherent characteristic; the Drude component is absent. With temperature decreasing, the Drude component develops and narrows rapidly. A well-defined plasma edge is observed in reflectance spectrum at temperature below 100 K, indicating a dramatically reduced scattering rate. The spectral weight contributed from free carriers is even smaller than that of FeSe single crystal. A number of phonon modes are visible in the measured spectra. We also observe clear spectral change below 160 cm^-1 at 10 K, associated with the formation of superconducting energy gap in the superconducting state. The energy scale of the superconducting gap is comparable to the value measured by angle-resolved photoemission spectroscopy technique. Like FeSe and other iron pnictides, a clear temperature-induced spectral weight transfer at high energy is observed for Li_0.8Fe_0.2ODFeSe, indicating the presence of strong correlation effect.