We present our results from time-domain THz spectroscopy measurements of thin films of mixed-valent YbAl\(_3\) and its structural analogue LuAl\(_3\). Combined with Fourier transform infrared (FTIR) spectroscopy, the extended Drude formalism is utilized to study the quasiparticle scattering rate and effective masses in YbAl\(_3\). We find that LuAl\(_3\) demonstrates conventional Drude transport whereas at low temperatures YbAl\(_3\) demonstrates a renormalized Drude peak and a mid-infrared (MIR) peak in the conductivity, indicative of the formation of a mass-enhanced Fermi liquid (FL). In YbAl\(_3\) the extended Drude analysis demonstrates consistency with FL behavior below the FL coherence temperature \(T^* < 40\) K with the scattering rate following \(T^2\) proportionality and a moderate mass enhancement. Despite not observing a clear \(\omega ^2\) Fermi liquid-like frequency dependence the evidence is consistent with a moderate mass Fermi liquid, albeit one with a smaller mass than observed in single crystals. The extended Drude analysis also demonstrates a slow crossover between the FL state and the normal state above the \(T^*\) in YbAl\(_3\), indicative of incoherent hybridization effects persisting to high temperatures.

我们介绍了混合价 YbAl \(_3\)及其结构模拟 LuAl \(_3\)薄膜的时域太赫兹光谱测量结果。结合傅里叶变换红外 (FTIR) 光谱，扩展的 Drude 形式用于研究 YbAl \(_3\) 中的准粒子散射率和有效质量。我们发现 LuAl \(_3\)表现出传统的德鲁德输运，而在低温下 YbAl \(_3\)表现出重新归一化的德鲁德峰和电导率中的中红外 (MIR) 峰，表明形成了质量增强费米液体 (FL)。在 YbAl \(_3\)扩展的 Drude 分析表明，在 FL 相干温度\(T^* < 40\) K以下与 FL 行为一致，散射率遵循\(T^2\)比例和中等质量增强。尽管没有观察到明显的\(\omega ^2\)费米液体样频率依赖性，但证据与中等质量的费米液体一致，尽管质量比在单晶中观察到的要小。扩展的 Drude 分析还证明了 FL 状态与YbAl \(_3\) 中\(T^*\)以上的正常状态之间的缓慢交叉，表明不连贯的杂交效应持续到高温。