Effective-mode representation of non-Markovian dynamics: a hierarchical approximation of the spectral density. II. Application to environment-induced nonadiabatic dynamics.
Effective-mode representation of non-Markovian dynamics: a hierarchical approximation of the spectral density. II. Application to environment-induced nonadiabatic dynamics.
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DOI：
10.1063/1.3226343
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
K. Hughes;Clara D. Christ;I. Burghardt
中科院分区：
文献类型：
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作者：
K. Hughes;Clara D. Christ;I. Burghardt
非马尔可夫方法在同伴论文中得到了发展[Hughes et al.， J. Chem.]物理学报，131,024109(2009)]，它采用了近似谱密度的分层序列，被扩展到耦合电子态的非绝热动力学的处理。我们关注自旋玻色子型哈密顿量，其中包括系统振动模的子集，这些模不进行任何近似处理，而一组槽模被转换为有效模链并在降维空间中处理。只有链的第一个成员与电子子系统耦合。链结构可以在连续的顺序上被截断，并通过作用于链末端的马尔可夫闭合来终止。从这种mori型构造中，得到了近似谱密度的层次结构，其精度越来越接近真实的熔池谱密度。介绍了由高频模和低频槽相互作用组成的振动子系统的动力学应用。槽对非绝热动力学有显著的影响，这可以在有效模态图中得到合理解释。构造了一个简化的二维子空间，描述了有效环境模诱导的非绝热过程的基本特征。发现电子相干在由有效模决定的最短时间尺度上保持，而退相干在更长的时间尺度上开始。数值模拟要么使用系统和整体槽的显式波函数表示，要么使用系统和有效模部分的显式表示，并结合Caldeira-Leggett主方程。
The non-Markovian approach developed in the companion paper [Hughes et al., J. Chem. Phys. 131, 024109 (2009)], which employs a hierarchical series of approximate spectral densities, is extended to the treatment of nonadiabatic dynamics of coupled electronic states. We focus on a spin-boson-type Hamiltonian including a subset of system vibrational modes which are treated without any approximation, while a set of bath modes is transformed to a chain of effective modes and treated in a reduced-dimensional space. Only the first member of the chain is coupled to the electronic subsystem. The chain construction can be truncated at successive orders and is terminated by a Markovian closure acting on the end of the chain. From this Mori-type construction, a hierarchy of approximate spectral densities is obtained which approach the true bath spectral density with increasing accuracy. Applications are presented for the dynamics of a vibronic subsystem comprising a high-frequency mode and interacting with a low-frequency bath. The bath is shown to have a striking effect on the nonadiabatic dynamics, which can be rationalized in the effective-mode picture. A reduced two-dimensional subspace is constructed which accounts for the essential features of the nonadiabatic process induced by the effective environmental mode. Electronic coherence is found to be preserved on the shortest time scale determined by the effective mode, while decoherence sets in on a longer time scale. Numerical simulations are carried out using either an explicit wave function representation of the system and overall bath or else an explicit representation of the system and effective-mode part in conjunction with a Caldeira-Leggett master equation.