Reassessing Graphene Absorption and Emission Spectroscopy
Reassessing Graphene Absorption and Emission Spectroscopy
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DOI：
10.1021/acs.nanolett.7b02500
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发表时间：
2017-10-01
期刊：
影响因子：
10.8
通讯作者：
Heller, Eric J.
中科院分区：
文献类型：
--
作者：
Yang, Yuan;Kolesov, Grigory;Heller, Eric J.
我们提出了一个新的范例，了解光吸收和热电子动力学实验在石墨烯。我们的分析重点分配适当的重要性声子辅助的间接过程和漂白的直接过程。我们显示了在紫外区的过量吸收的间接过程图。实验被认为表明电子和空穴的超快弛豫，在5-10 fs内从极非热分布达到热分布，而不是通过间接跃迁产生的新生电子和空穴分布来解释。这些不需要弛豫或自组织能量去除，以符合所观察到的发射光谱和快速脉冲吸收光谱。脉冲吸收后的快速发射主要由声子辅助过程控制，声子辅助过程的数量远远超过直接过程，并且总是可用，随时将任何电子与任何空穴连接起来。计算，包括明确计算间接过程的大小，支持这些观点。
We present a new paradigm for understanding optical absorption and hot electron dynamics experiments in graphene. Our analysis pivots on assigning proper importance to phonon-assisted indirect processes and bleaching of direct processes. We show indirect processes figure in the excess absorption in the UV region. Experiments which were thought to indicate ultrafast relaxation of electrons and holes, reaching a thermal distribution from an extremely nonthermal one in under 5-10 fs, instead are explained by the nascent electron and hole distributions produced by indirect transitions. These need no relaxation or ad-hoc energy removal to agree with the observed emission spectra and fast pulsed absorption spectra. The fast emission following pulsed absorption is dominated by phonon-assisted processes, which vastly outnumber direct ones and are always available, connecting any electron with any hole any time. Calculations are given, including explicitly calculating the magnitude of indirect processes, supporting these views.