Many recent experiments investigated potential and attractive means of modifying many-body interactions in two-dimensional materials through time-resolved spectroscopy techniques. However, the role of ultrafast phonon-assisted processes in two-dimensional systems is rarely discussed in depth. Here, we investigate the role of electron–phonon interaction in the transient optical absorption of graphene by means of first-principles methods. It is shown at equilibrium that the phonon-assisted transitions renormalize significantly the electronic structure. As a result, absorption peak around the Van-Hove singularity broadens and redshifts by ~100 meV. In addition, temperature increase and chemical doping are shown to notably enhance these phonon-assisted features. In the photoinduced transient response, we obtain spectral changes in close agreement with the experiments, and we associate them to the strong renormalization of occupied and unoccupied \(\pi\) bands, which predominantly comes from the coupling with the zone-center \({E}_{2g}\) optical phonon. Our estimation of the Coulomb interaction effects shows that the phonon-assisted processes can have a dominant role even in the subpicosecond regime.

许多最近的实验研究了通过时间分辨光谱技术修改二维材料中多体相互作用的潜在方法和有吸引力的方法。但是，很少深入讨论超快声子辅助过程在二维系统中的作用。在这里，我们通过第一原理方法研究电子-声子相互作用在石墨烯的瞬态光吸收中的作用。在平衡状态下显示，声子辅助的跃迁显着地使电子结构正常化。结果，Van-Hove奇点周围的吸收峰变宽并红移约100 meV。另外，显示出温度升高和化学掺杂显着增强了这些声子辅助特征。在光诱导的瞬态响应中，\（\ pi \）波段，主要来自与区域中心\（{E} _ {2g} \）光学声子的耦合。我们对库仑相互作用效应的估计表明，声子辅助过程甚至在亚皮秒范围内也可以起主导作用。