Visualizing coherent intermolecular dipole–dipole coupling in real space
Visualizing coherent intermolecular dipole–dipole coupling in real space
复制标题
DOI：
10.1038/nature17428
复制
发表时间：
2016-03
期刊：
影响因子：
64.8
通讯作者：
Yang Zhang;Yang Luo;Yao Zhang;Yun-Jie Yu;Yanmin Kuang;Li Zhang;Q. Meng;Yi Luo;Jinlong Yang-Jinlon
中科院分区：
文献类型：
--
作者：
Yang Zhang;Yang Luo;Yao Zhang;Yun-Jie Yu;Yanmin Kuang;Li Zhang;Q. Meng;Yi Luo;Jinlong Yang-Jinlon
在生物和人工系统中，许多重要的能量传递和光学过程都依赖于跨越几个发色团的激子耦合。这样的耦合原则上可以通过考虑所涉及的相干分子间偶极-偶极相互作用以直接的方式来描述。然而，在实践中，由于传统光学中的衍射极限，在真实的空间中直接观察相干偶极耦合和相关的激子离域是具有挑战性的。在这里，我们证明了高度本地化的激发，所产生的电子隧道从扫描隧道显微镜的尖端，结合所得的发光成像，可以用来映射的激子耦合在定义明确的安排的几个锌酞菁分子的空间分布。二聚体中激子的发光模式，记录不同的能量状态，发现类似于σ和π分子轨道，揭示了系统的局部光学响应和局部光学响应对二聚体中单个分子的过渡偶极的相对取向和相位的依赖性。我们产生了一个在线安排多达四个锌酞菁分子，具有更大的总跃迁偶极子，并表明，这导致在增强的“单分子”超辐射的低聚物后，位点选择性激发。这些发现表明，我们的实验方法提供了有关分子系统中相干偶极-偶极耦合的详细空间信息，这应该能够更好地理解和合理设计光捕获结构和量子光源。
Many important energy-transfer and optical processes, in both biological and artificial systems, depend crucially on excitonic coupling that spans several chromophores,,,,,,,,. Such coupling can in principle be described in a straightforward manner by considering the coherent intermolecular dipole–dipole interactions involved,. However, in practice, it is challenging to directly observe in real space the coherent dipole coupling and the related exciton delocalizations, owing to the diffraction limit in conventional optics. Here we demonstrate that the highly localized excitations that are produced by electrons tunnelling from the tip of a scanning tunnelling microscope, in conjunction with imaging of the resultant luminescence, can be used to map the spatial distribution of the excitonic coupling in well-defined arrangements of a few zinc-phthalocyanine molecules. The luminescence patterns obtained for excitons in a dimer, which are recorded for different energy states and found to resembleσandπmolecular orbitals, reveal the local optical response of the system and the dependence of the local optical response on the relative orientation and phase of the transition dipoles of the individual molecules in the dimer. We generate an in-line arrangement up to four zinc-phthalocyanine molecules, with a larger total transition dipole, and show that this results in enhanced ‘single-molecule’ superradiance from the oligomer upon site-selective excitation. These findings demonstrate that our experimental approach provides detailed spatial information about coherent dipole–dipole coupling in molecular systems, which should enable a greater understanding and rational engineering of light-harvesting structures and quantum light sources.