Detection of the energy conversion pathways between photons, charge carriers, and the lattice is of fundamental importance to understand fundamental physics and to advance materials and devices. Yet, such insight remains incomplete due to experimental challenges in disentangling the various signatures on overlapping timescales. Here, we show that attosecond core-level x-ray absorption fine-structure spectroscopy (XANES) meets this challenge by providing an unambiguous and simultaneous view on the temporal evolution of the photon-carrier-phonon system. We provide surprising new results by applying the method to graphite, a seemingly well-studied system whose investigation is complicated by a variety of mechanisms occurring across a wide range of temporal scales. The simultaneous real-time measurement of electrons and holes reveals disparate scattering mechanisms for infrared excitation close to the Fermi energy. We find that ultrafast dephasing of the coherent carrier dynamics is governed by impact excitation (IE) for electrons, while holes exhibit a switchover from impact excitation to Auger heating (AH) already during the 11-fs duration of the infrared light field. We attribute this switchover to the limited scattering phase space in the $n$-doped material. We further elucidate the excitation mechanisms of strongly coupled optical phonons (SCOPs). The coherent excitation of both SCOPs is nondisplacive and is explained by the strong electron-phonon scattering, i.e., via a seemingly incoherent process. We identify the $A_1^{\prime }$ phonon as the dominating channel for dissipation of electronic coherence. Moreover, unobserved in graphite, we find high-frequency oscillations up to 90 THz, which arise from the modulation of the electronic density of states by the atomic displacements along the $E_{2g}$ and $A_1^{\prime }$ modes. These measurements establish the utility of core-level XANES with attosecond temporal resolution to achieve an unambiguous and simultaneous view on the temporal evolution of the photon-carrier-phonon system with surprising new results even for a seemingly well-studied system like graphite. While the graphite measurement was conducted around the $K$ edge of carbon, adapting the methodology to other materials only requires spectra coverage of the respective elemental edge of the material’s constituent. This flexibility makes our methodology widely applicable to detect and distinguish the various dynamic contributions to the flow of energy inside materials on their native timescales.

中文翻译：

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使用阿秒核心级光谱实时探测光、载流子和晶格之间的能量转换途径

电子和空穴的同时实时测量揭示了接近费米能量的红外激发的不同散射机制。我们发现相干载流子动力学的超快移相由电子的冲击激发 (IE) 控制，而在红外光场的 11-fs 持续时间内，空穴表现出从冲击激发到俄歇加热 (AH) 的转换。我们将这种转换归因于有限的散射相空间$n$-掺杂材料。我们进一步阐明了强耦合光学声子 (SCOP) 的激发机制。两个 SCOP 的相干激发是非位移的，可以通过强电子-声子散射来解释，即通过看似不相干的过程。我们确定${\mathrm{一个}}_1^{\prime }$声子作为电子相干耗散的主要通道。此外，在石墨中未观察到，我们发现高达 90 THz 的高频振荡，这是由沿原子位移的电子态密度调制引起的。${乙}_{2G}$ 和 ${\mathrm{一个}}_1^{\prime }$模式。这些测量建立了具有阿秒时间分辨率的核心级 XANES 的效用，以实现对光子 - 载流子 - 声子系统的时间演化的明确且同步的观点，即使对于像石墨这样看似经过充分研究的系统，也能获得令人惊讶的新结果。虽然石墨测量是在周围进行的$钾$碳的边缘，将该方法应用于其他材料只需要材料成分的各个元素边缘的光谱覆盖。这种灵活性使我们的方法广泛适用于检测和区分对材料内部能量流动在其原始时间尺度上的各种动态贡献。