Current advances in ultrafast electron microscopy make it possible to combine optical pumping of a nanostructure and electron beam probing with sub-Ångstrom and femtosecond spatiotemporal resolution. We present a theory predicting that this technique can reveal a rich out-of-equilibrium dynamics of plasmon excitations in graphene and graphite samples. In a disruptive departure from the traditional probing of nanoscale excitations based on the identification of spectral features in the transmitted electrons, we show that the measurement of angle-resolved, energy-integrated inelastic electron scattering can trace the temporal evolution of plasmons in these structures and provide momentum-resolved mode identification, thus avoiding the need for highly monochromatic electron beams and the use of electron spectrometers. This previously unexplored approach to study the ultrafast dynamics of optical excitations can be of interest to understand and manipulate polaritons in 2D semiconductors and other materials exhibiting a strong thermo-optical response.

中文翻译：

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超快动量分辨的自由电子探测的光学泵浦等离子体热力学

超快电子显微镜的最新进展使得将纳米结构的光泵浦和电子束探测与亚埃和飞秒时空分辨率相结合成为可能。我们提出了一种理论，预测该技术可以揭示石墨烯和石墨样品中等离激元激发的丰富的失衡动力学。与基于透射电子中光谱特征的识别的纳米级激发的传统探测的破坏性偏离，我们表明，角分辨，能量积分的非弹性电子散射的测量可以追踪这些结构中等离激元的时间演化，并且提供动量分辨的模式识别，从而避免了对高度单色电子束的需要和电子光谱仪的使用。