Huang Zhongkai, Wang Lu, Wu Changqin, Chen Lipeng, Grossmann Frank, Zhao Yang
Division of Materials Science, Nanyang Technological University, Singapore, Singapore.
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
Phys Chem Chem Phys. 2017 Jan 4;19(2):1655-1668. doi: 10.1039/c6cp07107d.
Treated traditionally by the Ehrenfest approximation, the dynamics of a one-dimensional molecular crystal model with off-diagonal exciton-phonon coupling is investigated in this work using the Dirac-Frenkel time-dependent variational principle with the multi-DAnsatz. It is shown that the Ehrenfest method is equivalent to our variational method with the single DAnsatz, and with the multi-DAnsatz, the accuracy of our simulated dynamics is significantly enhanced in comparison with the semi-classical Ehrenfest dynamics. The multi-DAnsatz is able to capture numerically accurate exciton momentum probability and help clarify the relation between the exciton momentum redistribution and the exciton energy relaxation. The results demonstrate that the exciton momentum distributions in the steady state are determined by a combination of the transfer integral and the off-diagonal coupling strength, independent of the excitonic initial conditions. We also probe the effect of the transfer integral and the off-diagonal coupling on exciton transport in both real and reciprocal space representations. Finally, the variational method with importance sampling is employed to investigate temperature effects on exciton transport using the multi-DAnsatz, and it is demonstrated that the variational approach is valid in both low and high temperature regimes.
传统上采用埃伦费斯特近似处理，本文利用具有多D安萨茨的狄拉克 - 弗伦克尔含时变分原理研究了具有非对角激子 - 声子耦合的一维分子晶体模型的动力学。结果表明，埃伦费斯特方法等同于我们采用单D安萨茨的变分方法，并且采用多D安萨茨时，与半经典埃伦费斯特动力学相比，我们模拟动力学的精度显著提高。多D安萨茨能够数值精确地捕捉激子动量概率，并有助于阐明激子动量再分布与激子能量弛豫之间的关系。结果表明，稳态下的激子动量分布由转移积分和非对角耦合强度共同决定，与激子初始条件无关。我们还在实空间和倒易空间表示中探究了转移积分和非对角耦合对激子输运的影响。最后，采用具有重要性抽样的变分方法，利用多D安萨茨研究温度对激子输运的影响，结果表明变分方法在低温和高温区域均有效。
