Real-Time TDDFT Investigation of Optical Absorption in Gold Nanowires
Real-Time TDDFT Investigation of Optical Absorption in Gold Nanowires
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DOI：
10.1021/acs.jpcc.9b00296
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发表时间：
2019-06-13
影响因子：
3.7
通讯作者：
Aikens, Christine M.
中科院分区：
文献类型：
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作者：
Senanayake, Ravithree D.;Lingerfelt, David B.;Aikens, Christine M.
用实时TDDFT方法研究了一组线性金纳米线Au-m(m=4，6，8，10，12)的等离子体激元行为。以前已经通过线性响应TDDFT计算研究了金纳米线的这些特征激发，并对这两种方法的结果进行了比较。实时TDDFT提供了有关在这些系统中的激发过程中电子布居如何变化的动态信息。本研究还研究了金纳米线中d带跃迁与类等离子体激元状态之间的关系。在这项工作中，研究了偶极激发后的纵向和横向吸收峰，并考察了改变纳米线长度的影响。还研究了模型金纳米线等离子体激元类激发过程中单粒子跃迁的时间演化和不同跃迁之间的相互作用。在光吸收光谱中，最低能量的纵向激发出现在1-2 eV附近；该峰随着纳米线长度的增加而红移。由于带间跃迁的参与，出现了纵向峰的分裂。横模的频率在吸收光谱中约为6-7 eV，随着纳米线长度的增加趋于恒定。随时间变化的占位数及其傅里叶变换谱表明，在纵向峰中可以识别出占主导地位的单粒子跃迁(Sigma(N)->；Sigma(n+1))，它与较不可能的d带跃迁(d->；Sigma)相耦合。相反，横模是由具有Sigma(N)->；PI(N)特征的两个或多个单粒子跃迁耦合而成的。
Using a real-time TDDFT method, a set of linear gold nanowires Au-m (m = 4, 6, 8, 10, 12) are investigated to understand the plasmon-like behavior that results from resonant excitation of a superposition of single-electron transitions. These characteristic excitations of gold nanowires have been previously investigated via linear-response TDDFT calculations, and the results from these two approaches are compared. Real-time TDDFT provides dynamical information about how the electron populations change during excitations in these systems. This study also investigates the relationship between the d-band transitions and the plasmon-like states in gold nanowires. In this work, the longitudinal and transverse absorption peaks are studied after dipolar excitation, and the effects of changing the length of the nanowire are examined. The time evolution of the single-particle transitions and the interplay between different transitions involved in the plasmon-like excitations of model gold nanowires are also investigated. The lowest-energy longitudinal excitation occurs around 1-2 eV in the optical absorption spectra; this peak redshifts with increasing nanowire length. A splitting in the longitudinal peak is present due to the involvement of interband transitions. The frequency of the transverse mode, which lies around 6-7 eV in the absorption spectra, tends to stay constant as the nanowire length increases. The time-dependent occupation numbers and their Fourier transformed spectra reveal that a dominant single-particle transition (Sigma(n) ->Sigma(n+1)) can be identified in the longitudinal peaks, which is coupled with less probable d-band transitions (d -> Sigma). In contrast, the transverse modes are constructed from a coupling of two or more single-particle transitions with a Sigma(n) -> Pi(n) character.