Polaronic quasiparticle picture for generation dynamics of coherent phonons in semiconductors: Transient and nonlinear Fano resonance
Polaronic quasiparticle picture for generation dynamics of coherent phonons in semiconductors: Transient and nonlinear Fano resonance
复制标题
用于半导体中相干声子生成动力学的极化准粒子图：瞬态和非线性法诺共振
DOI：
10.1103/physrevb.95.014301
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发表时间：
2017
影响因子：
3.7
通讯作者：
and Nobuya Maeshima
中科院分区：
文献类型：
--
作者：
Yohei Watanabe;Ken-ichi Hino;Muneaki Hase;and Nobuya Maeshima
基于极化准粒子（PQ）模型，我们研究了极性和非极性半导体（如GaAs和Si）中相干声子的产生动力学。在这个模型中，PQ算符由两种算符组成：一种是准玻色子算符，定义为一组电子算符对的线性组合，另一种是纵向光学（LO）声子算符。特别地，解决了瞬态和非线性Fano共振（FR）问题，其中仅在轻掺杂Si中观察到这种量子干涉效应的痕迹，该效应在载流子被超短脉冲激光激发后立即发生[M. Hase，Nature（伦敦）426，51（2003）NATUAS 0028 -083610.1038/nature 02044]，尽管尚未在GaAs中观察到。PQ模型使我们能够直截了当地表明，声子的能量状态是嵌入在由一组绝热本征态的准玻色子形成的连续态，这种能量配置是在目前的光学非线性系统中的瞬态FR的表现形式的必要条件。数值计算了瞬态光激发态的延迟纵向介电函数相关的光电子谱和LO声子位移时间函数相关的功率谱。光电子能谱表明，在未掺杂的Si中，在瞬时载流子激发后立即出现FR的非对称谱线特征，并逐渐衰减，而在未掺杂的GaAs中，在整个时域内没有出现光谱的非对称性。在功率谱中也得到了类似的结果。这些结果与文献报道的实验结果一致。结果发现，所获得的光谱轮廓之间的差异，未掺杂的Si和GaAs是归因于LO声子和准玻色子之间的有效相互作用的相位因子。文中对FR动力学进行了更详细的讨论。
We examine generation dynamics of coherent phonons in both polar and nonpolar semiconductors, such as GaAs and Si, based on a polaronic-quasiparticle (PQ) model. In this model, the PQ operator is composed of two kinds of operators: one is a quasiboson operator, defined as a linear combination of a set of pairs of electron operators, and the other is a longitudinal optical (LO) phonon operator. In particular, the problem of transient and nonlinear Fano resonance (FR) is tackled, where the vestige of this quantum interference effect was observed exclusively in lightly-doped Si immediately after carriers were excited by an ultrashort pulse laser [M. Hase , Nature (London) 426, 51 (2003)NATUAS0028-083610.1038/nature02044], although not observed yet in GaAs. The PQ model enables us to show straightforwardly that the phonon energy state is embedded in continuum states formed by a set of adiabatic eigenstates of the quasiboson; this energy configuration is a necessary condition of the manifestation of the transient FR in the present optically nonlinear system. Numerical calculations are done for photoemission spectra relevant to the retarded longitudinal dielectric function of transient photoexcited states and for power spectra relevant to the LO-phonon displacement function of time. The photoemission spectra show that in undoped Si, an asymmetric spectral profile characteristic of FR comes into existence immediately after the instantaneous carrier excitation to fade out gradually, whereas in undoped GaAs, no asymmetry in spectra appears in the whole temporal region. The similar results are also obtained in the power spectra. These results are in harmony with the reported experimental results. It is found that the obtained difference in spectral profile between undoped Si and GaAs is attributed to a phase factor of an effective interaction between the LO phonon and the quasiboson. More detailed discussion of the FR dynamics is made in the text.