Direct determination of mode-projected electron-phonon coupling in the time domain
Direct determination of mode-projected electron-phonon coupling in the time domain
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DOI：
10.1126/science.aaw1662
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发表时间：
2019-12-06
期刊：
影响因子：
56.9
通讯作者：
Damascelli, A.
中科院分区：
文献类型：
--
作者：
Na, M. X.;Mills, A. K.;Damascelli, A.
超快光谱已成为阐明量子材料的微观描述和动力学性质的重要工具。特别是，通过跟踪非热电子的动力学，可以揭示材料的主要散射过程。在这里，我们提出了一种使用时间和角度分辨光电子能谱（TR-ARPES）提取时域中电子-声子耦合强度的方法。这种方法在石墨中得到了证明，我们研究了 K 点光注入电子的动力学，检测与强耦合光学声子发射相对应的量化能量损失过程。我们表明，观察到的由声子散射过程介导的光谱权重转移的特征时间尺度允许直接定量提取特定模式的电子声子矩阵元素。
Ultrafast spectroscopies have become an important tool for elucidating the microscopic description and dynamical properties of quantum materials. In particular, by tracking the dynamics of nonthermal electrons, a material's dominant scattering processes can be revealed. Here, we present a method for extracting the electron-phonon coupling strength in the time domain, using time- and angle-resolved photoemission spectroscopy (TR-ARPES). This method is demonstrated in graphite, where we investigate the dynamics of photoinjected electrons at the K point, detecting quantized energy-loss processes that correspond to the emission of strongly coupled optical phonons. We show that the observed characteristic time scale for spectral weight transfer mediated by phonon-scattering processes allows for the direct quantitative extraction of electron-phonon matrix elements for specific modes.