Hot carrier dynamics and electron-optical phonon coupling in photoexcited graphene via time-resolved ultrabroadband terahertz spectroscopy
Hot carrier dynamics and electron-optical phonon coupling in photoexcited graphene via time-resolved ultrabroadband terahertz spectroscopy
复制标题
通过时间分辨超宽带太赫兹光谱研究光激发石墨烯中的热载流子动力学和电子光声子耦合
DOI：
10.1103/physrevresearch.3.043143
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发表时间：
2021
影响因子：
4.2
通讯作者：
and Masatsugu Yamashita
中科院分区：
文献类型：
--
作者：
Sho Ikeda;Chiko Otani;and Masatsugu Yamashita
电子-电子相互作用是量子场论中狄拉克费米子对数重整化的一个重要来源。电子-电子相互作用引起的电子-光学声子耦合（EPC）重正化在热载流子和声子动力学中起着关键作用，自石墨烯被发现以来，人们一直在讨论这一问题。我们调查热载流子动力学和EPC强度使用时间分辨超宽带太赫兹（THz）光谱结合数值模拟的基础上玻尔兹曼输运方程和一个全面的温度模型。数值模拟表明，载流子屏蔽效应显著抑制了杂质和表面极性声子的库仑势对非本征载流子的散射，对重掺杂石墨烯/聚对苯二甲酸乙二酯（PET）衬底的太赫兹光电导的贡献可以忽略不计.在高泵浦能量密度下，THz电导谱出现了较大的负光电导和非Drude行为，这是由热载流子分布和散射率随时间的变化引起的。瞬态反射率很好地反映了EPC强度和时间演化的热载流子和光学声子动力学。通过太赫兹电导率谱的拟合和瞬态太赫兹反射率的时间演化，我们成功地估计了该点附近光学声子模的EPC矩阵元。相应的无量纲EPC常数Fermi能量Δ F=0.43eV比考虑PET衬底的介电屏蔽效应的重整化群方法的预测值稍大。这导致了显着的差异，热载流子和声子动力学相比，没有重整化效应的e-e相互作用。这种方法可以提供热载流子和光学声子动力学的定量理解，并支持未来石墨烯光电器件的发展。
Electron-electron (e-e) interaction is known as a source of logarithmic renormalizations for Dirac fermions in quantum field theory. The renormalization of electron-optical phonon coupling (EPC) by e-e interaction, which plays a pivotal role in hot carrier and phonon dynamics, has been discussed since the discovery of graphene. We investigate hot carrier dynamics and EPC strength using time-resolved ultrabroadband terahertz (THz) spectroscopy combined with numerical simulation based on the Boltzmann transport equation and a comprehensive temperature model. The numerical simulation demonstrates that the extrinsic carrier scatterings by the Coulomb potential of the charged impurity and surface polar phonons are significantly suppressed by the carrier screening effect and have negligible contributions to the THz photoconductivity in heavily doped graphene on polyethylene terephthalate (PET) substrate. The large negative photoconductivity and the non-Drude behavior of THz conductivity spectra appear under high pump fluence and can be attributed to the temporal variation of the hot carrier distribution and scattering rate. The transient reflectivity well reflects the EPC strength and temporal evolution of the hot carrier and optical phonon dynamics. We successfully estimate the EPC matrix element of theoptical phonon mode near thepoint asfrom the fitting of THz conductivity spectra and temporal evolution of transient THz reflectivity. The corresponding dimensionless EPC constantat Fermi energy ɛF=0.43eV is slightly larger than the prediction of the renormalization group approach including the dielectric screening effect of the PET substrate. This leads to a significant difference in hot carrier and phonon dynamics compared with those without the renormalization effect by the e-e interaction. This approach can provide a quantitative understanding of hot carrier and optical phonon dynamics and support the development of future graphene optoelectronic devices.