The measurement and manipulation of the coherent dynamics of excitonic states constitute a forefront research challenge in semiconductor optics and quantum-coherence-based protocols for optoelectronic technologies. Layered semiconductors have emerged as an ideal platform for the study of exciton dynamics with accessible and technologically relevant energy and time scales. Here, we investigate the subpicosecond exciton dynamics in a van der Waals semiconductor upon quasi-resonant excitation and achieve to single out an incipient coherent excitonic state. Combining broad-band transient reflectance spectroscopy and simulations based on many-body perturbation theory, we reveal a transient enhancement of the excitonic line intensity that originates from photoinduced coherent polarization that is phase-locked with the interacting electromagnetic field. This finding allows us to define the spectral signature of a coherent excitonic state and to experimentally track the dynamical crossover from coherent to incoherent exciton, unlocking the prospective optical control of an exciton population on the intrinsic quantum-coherence time scale.

中文翻译：

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层状半导体 BiI3 中相干激子态的检测


激子态相干动力学的测量和操纵构成了半导体光学和基于量子相干的光电技术协议的前沿研究挑战。层状半导体已成为研究激子动力学的理想平台，具有可访问且技术相关的能量和时间尺度。在这里，我们研究了准谐振激发下范德华半导体中的亚皮秒激子动力学，并实现了挑选出初始相干激子态。结合宽带瞬态反射光谱和基于多体微扰理论的模拟，我们揭示了源自与相互作用的电磁场锁相的光致相干偏振的激子线强度的瞬态增强。这一发现使我们能够定义相干激子态的光谱特征，并通过实验跟踪从相干激子到非相干激子的动态交叉，解锁激子群体在内在量子相干时间尺度上的前瞻性光学控制。