arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2002.09418physics.chem-phphysics.atm-clusphysics.atom-ph
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热运动分子聚集体中的激发输运

Excitation Transport in Molecular Aggregates with thermal motion

R. Pant, S. Wüster

摘要:

在一定条件下,分子聚集体可以通过偶极-偶极相互作用将电子激发能传输到很远的距离。在这里,我们探讨在何种程度上整个单体的热运动可以引导或增强这种激发运输。这种运动引起聚集体几何结构的变化,从而改变激子态。在某些条件下,激发能因此可以由聚集体折射地传输,遵循一定的激子本征态。虽然这样的运输总是慢于直接迁移通过偶极-偶极相互作用,我们表明,通过运动的运输可以产生更高的运输效率,在现场的能量紊乱的存在下,比静态对应。为此,我们考虑两个简单的模型的分子运动:(i)纵向振动的单体沿聚集方向内的分子间的结合潜力和(ii)扭转运动的平面单体在一个平面正交的聚集方向。所使用的参数和潜在的形状是相关的染料分子聚集体。我们采用量子经典方法,其中分子通过简化的经典分子动力学运动,而激发输运处理量子力学使用薛定谔方程。对于这两种模型,我们发现参数制度中的运动增强激发运输,然而,这些是更现实的扭转的情况下,由于有限的运动范围内的一个典型的莫尔斯型分子间的潜力。我们最后表明,传输增强可以联系到绝热量子动力学。这种通过绝热运动的输运增强似乎是一个有用的资源,以打击激子捕获的混乱。

英文摘要:

Molecular aggregates can under certain conditions transport electronic excitation energy over large distances due to dipole-dipole interactions. Here, we explore to what extent thermal motion of entire monomers can guide or enhance this excitation transport. The motion induces changes of aggregate geometry and hence modifies exciton states. Under certain conditions, excitation energy can thus be transported by the aggregate adiabatically, following a certain exciton eigenstate. While such transport is always slower than direct migration through dipole-dipole interactions, we show that transport through motion can yield higher transport efficiencies in the presence of on-site energy disorder than the static counterpart. For this we consider two simple models of molecular motion: (i) longitudinal vibrations of the monomers along the aggregation direction within their inter-molecular binding potential and (ii) torsional motion of planar monomers in a plane orthogonal to the aggregation direction. The parameters and potential shapes used are relevant to dye-molecule aggregates. We employ a quantum-classical method, in which molecules move through simplified classical molecular dynamics, while the excitation transport is treated quantum mechanically using Schrödinger's equation. For both models we find parameter regimes in which the motion enhances excitation transport, however these are more realistic for the torsional scenario, due to the limited motional range in a typical Morse type inter-molecular potential. We finally show that the transport enhancement can be linked to adiabatic quantum dynamics. This transport enhancement through adiabatic motion appears a useful resource to combat exciton trapping by disorder.

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