The weakest mode of the infrared active folded phonons in 4H–SiC, folded transverse acoustic (FTA) mode, has been experimentally studied. The lifetime of the FTA phonons has been determined. The lifetime is 58 ± 4 ps at room temperature and increases to 140 ± 7 ps when the temperature is decreased to 5 K. These results were obtained by the experimental study of far-infrared transmission of the SiC crystal and its theoretical simulation using an oscillator model for the dielectric function around the phonon resonance. The FTA phonon lifetime was a fitting parameter of the model when analyzing the irregular interference pattern in the transmission spectrum measured with a high resolution (0.2 cm−1). Oscillator strength of the FTA phonon resonance has also been determined. It is equal to (6.0 ± 0.5 ) × 10 − 4 and does not depend on temperature.

中文翻译：

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4H-SiC中折叠横向声子的远红外光谱

已经通过实验研究了 4H-SiC 中红外有源折叠声子的最弱模式折叠横向声学 (FTA) 模式。FTA 声子的寿命已经确定。寿命在室温下为 58 ± 4 ps，当温度降低到 5 K 时增加到 140 ± 7 ps。 这些结果是通过对 SiC 晶体的远红外传输的实验研究和使用振荡器的理论模拟获得的声子共振周围的介电函数模型。在分析以高分辨率 (0.2 cm-1) 测量的透射光谱中的不规则干涉图案时，FTA 声子寿命是模型的拟合参数。FTA 声子共振的振荡器强度也已确定。它等于 (6.0 ± 0.5 ) × 10 − 4 并且不依赖于温度。