Nonthermal Dynamics of Dielectric Functions in a Resonantly Bonded Photoexcited Material
Nonthermal Dynamics of Dielectric Functions in a Resonantly Bonded Photoexcited Material
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DOI：
10.1002/adfm.202002821
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发表时间：
2020-06
影响因子：
19
通讯作者：
H. Tanimura;S. Watanabe;T. Ichitsubo
中科院分区：
文献类型：
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作者：
H. Tanimura;S. Watanabe;T. Ichitsubo
飞秒激光激发下的超快相变是热相变还是非热相变，一直是人们争论的一个基本问题。其中的困难之一是如何考虑光激发系统的热化，其中“晶格”和“电子”系统在光激发之后从平衡状态解耦。这项工作显示了一种方法来识别光激发半导体的热化时间域，其中可以通过监测时间分辨的光吸收宽带光谱并将其与热诱导光谱变化进行比较来检测，通过该方法，PbTe的电子晶格热化时间被评估为12 ps。进一步分析动态介电函数证实了热化时间与谐振键合的恢复时间有关。这样一个关键的热化时间的确定将消除的不确定性的“热或非热”的超快相变的共振键合材料。
A fundamental question of whether it is thermal or nonthermal has often been argued, when the system undergoes an ultrafast phase change by femtosecond laser photoexcitation. One of the difficulties therein is how to consider the thermalization of a photoexcited system, in which the “lattice” and “electron” systems are decoupled from an equilibrium state just after photoexcitation. This work shows a methodology to identify a thermalization‐time domain of a photoexcited semiconductor, where it can be detected by monitoring the time‐resolved photoabsorption broadband spectrum and comparing that to thermally induced spectrum changes, by which the electron–lattice thermalization time is evaluated to be 12 ps for PbTe. Further analyzing the dynamic dielectric functions substantiates that thermalization time is related to the recovery time of the resonant bonding. Such a crucial determination of thermalization time would eliminate an uncertainty of “thermal or nonthermal” in ultrafast phase change of the resonantly bonded materials.