标题： 通过超快光谱技术解析半导体中的能量流机制：以锗为例 显示英文标题

标题： Unraveling energy flow mechanisms in semiconductors by ultrafast spectroscopy: Germanium as a case study

摘要： 半导体材料是现代电子学的基础，其功能由在（亚）皮秒时间尺度上发生的基元激发之间的相互作用决定。 使用时间分辨拉曼光谱和瞬态反射率测量，我们揭示了锗中的超快动力学。 我们在最初的几个皮秒内观察到光学声子温度的增加，这是由光激发空穴的能量传递驱动的，并随后通过非谐耦合衰减到声学声子。 此外，这种声子模式的温度、拉曼频率和线宽表现出显著不同的衰减动力学。 这种差异归因于超快激发产生的局部热应变。 我们还观察到布里渊振荡，这是通过锗传播的应变脉冲，其衰减与光学声子模式相关。 这些发现得到了密度泛函理论和分子动力学模拟的支持，为半导体中的能量耗散机制提供了更好的理解。 显示英文摘要

摘要： Semiconductor materials are the foundation of modern electronics, and their functionality is dictated by the interactions between fundamental excitations occurring on (sub-)picosecond timescales. Using time-resolved Raman spectroscopy and transient reflectivity measurements, we shed light on the ultrafast dynamics in germanium. We observe an increase in the optical phonon temperature in the first few picoseconds, driven by the energy transfer from photoexcited holes, and the subsequent decay into acoustic phonons through anharmonic coupling. Moreover, the temperature, Raman frequency, and linewidth of this phonon mode show strikingly different decay dynamics. This difference was ascribed to the local thermal strain generated by the ultrafast excitation. We also observe Brillouin oscillations, given by a strain pulse traveling through germanium, whose damping is correlated to the optical phonon mode. These findings, supported by density functional theory and molecular dynamics simulations, provide a better understanding of the energy dissipation mechanisms in semiconductors.