The ultrafast optical dynamics in solution-processed ${\rm PbI}_2$ film on quartz substrate around the band edge have been systematically studied by transient reflectance spectroscopy and femtosecond resolved Kerr rotation spectroscopy at room temperature. The Kerr rotation angle shows a maximum at the excitonic photobleaching peak and increases with the pump fluence until reaching a saturation value of ${\sim}{0.8}\;{\rm deg}$ (${\sim}{4}\;{\rm deg}/\unicode{x00B5}{\rm m}$), which is on the same order as that for ${\rm CH}_3{\rm NH}_3{\rm PbI}_3$ perovskite film. The spin lifetime gradually decreases from 2.24 to 0.48 ps when increasing the pump fluence from 13 to ${234}\;\unicode{x00B5} {{{\rm J}/{\rm cm}}^2}$, which is attributed to the strong spin-orbital coupling and the dominance of the Elliot–Yafet process in spin relaxation. Our findings suggest that ${\rm PbI}_2$ film is a promising candidate for ultrafast spin switching with a subpicosecond time scale and optical isolator in optical communications owing to the giant rotation angle.

中文翻译：

---

通过克尔旋转技术在 PbI ₂薄膜中探测亚皮秒磁光响应

在室温下，通过瞬态反射光谱和飞秒分辨克尔旋转光谱，系统研究了溶液处理的${\rm PbI}_2$膜在带边缘周围的石英衬底上的超快光学动力学。克尔旋转角在激子光漂白峰值处显示最大值，并随着泵注量的增加而增加，直到达到饱和值${\sim}{0.8}\;{\rm deg}$ ( ${\sim}{4}\ ;{\rm deg}/\unicode{x00B5}{\rm m}$ )，与${\rm CH}_3{\rm NH}_3{\rm PbI}_3$钙钛矿的顺序相同电影。当泵注量从 13 增加到${234}\;\unicode{x00B5} {{{\rm J}/{\rm cm}}^2}$时，自旋寿命从 2.24 ps 逐渐降低到 0.48 ps，这归因于强自旋轨道耦合和 Elliot-Yafet 过程在自旋弛豫中的主导地位。我们的研究结果表明，由于巨大的旋转角，${\rm PbI}_2$薄膜是具有亚皮秒时间尺度的超快自旋切换和光通信中的光隔离器的有希望的候选者。