Real-time observations of the coherent electron dynamics induced by ultrashort light pulses in condensed-matter systems have remained elusive due to limitations in existing attosecond devices. Here we show that attosecond transient absorption resulting from an IR-pump/x-ray probe numerical experiment performed in graphene unambiguously encodes the information of the coherent electron dynamics induced by the pump pulse. First, we demonstrate the possibility of tracking in real time the electron injection through the Dirac points. Second, we derive and demonstrate a simple semiclassical theory that correlates the energy structure and the action Berry phase with strong changes in the absorption spectrum around Van Hove singularities. Our work opens the way to the development of novel imaging techniques in condensed matter systems at the attosecond timescale.

中文翻译：

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石墨烯中的阿秒X射线瞬态吸收光谱

由于现有的阿秒装置的局限性，在凝聚态系统中由超短光脉冲引起的相干电子动力学的实时观测仍然难以捉摸。在这里，我们表明，由在石墨烯中进行的IR泵/ x射线探针数值实验得出的阿秒瞬态吸收明确地编码了由泵浦脉冲引起的相干电子动力学的信息。首先，我们证明了实时跟踪通过狄拉克点的电子注入的可能性。其次，我们推导并证明了一个简单的半经典理论，该理论将能量结构和作用贝里相与范霍夫奇异点周围的吸收光谱的强烈变化相关联。