We study the thermal relaxation of interlayer excitons from the free to momentary self-trapped states in lead halide perovskite van der Waals heterostructures based on the well-known Huang-Rhys model. We find that these relaxation processes (self-trapped processes) are very fast ranging from nanoseconds to picoseconds. Moreover, the self-trapped time displays different variational trends by regulating three key structural parameters of the heterostructure, which could be intrinsically attributed to the modulation of exciton–phonon coupling by these structural parameters, resulting in the variation of the self-trapping depth. The underlying physical pictures that the changing of intersection points of two adiabatic potential between the free and momentary self-trapped states in the configuration coordinates are proposed to explain these relaxation processes. These results not only provide the significant enlightenments for analyzing the abnormal features of excitonic spectra in experiments but also present the practical ways to modulate the dynamical processes of excitons in two-dimensional structures.

中文翻译：

---

卤化铅钙钛矿范德华异质结构中层间激子从自由态到自捕获态的快速弛豫

我们基于著名的黄里斯模型研究了卤化铅钙钛矿范德华异质结构中层间激子从自由态到瞬时自陷态的热弛豫。我们发现这些弛豫过程（自陷过程）非常快，从纳秒到皮秒不等。此外，通过调节异质结构的三个关键结构参数，自捕获时间呈现出不同的变化趋势，这本质上可以归因于这些结构参数对激子-声子耦合的调制，从而导致自捕获深度的变化。提出了配置坐标中自由态和瞬时自陷态之间两个绝热势交点变化的基本物理图像来解释这些弛豫过程。这些结果不仅为分析实验中激子谱的异常特征提供了重要启示，而且为调控二维结构中激子的动力学过程提供了实用方法。