二能级集光化合物系统的动力学行为研究

The high efficiency of energy transport is a quantum behavior in light-harvesting complexes. The key is to consider the exciton''s dynamical properties and the quantum coherence''s effects on the transport efficiency. Generally, the spin-boson model in physics can be applied to simulate the system. Therefore, some physical concepts, such as quantum coherence, quantum entanglement, quantum phase transition, dephasing and decoherece, etc., have been introduced in the photosynthesis systems. Then the corresponding studies and discussions were extensively in progress. In addition, some experiments, such as the coherence experiment of exciton, superradiance phenomenon and two-dimensional optical spectroscopy experiments,etc., reflect the coherence of the system directly. It also exhibits the relation between the quantum coherence and the high transport efficiency. However, some physical phenomena are still in debate in a lot of theoretical researches. For example, it is an issue whether the quantum coherence must be a decisive factor in maintaining the high transport efficiency. On the other hand, some physical pictures are still in lack in the present studies, such as the exciton transport effects in different phase regime with the occurrence of quantum phase transition, the studies of two-dimensional optical spectroscopy and quantum entanglement in light-harvesting complexes system with an external electric field, the dynamical evolvement of multi-excitons in the system, and so on. In all, the aims of the project are to help the further understanding the nature of quantum dynamics of light-harvesting complexes system. It has the important theoretical significance for improving the energy transport efficiency of the biological transmission systems.

集光化合物高效率的能量输运表现为一种量子行为，其关键是考虑激子在其中的动力学行为及量子相干对其输运效率的影响。一般情况下，用物理中的自旋波色模型就能很好地模拟该系统。基于此，一些的物理概念如量子相干、量子纠缠，量子相变，退位相、退相干等，已经在光合作用体系被广泛研究及探讨。另外，一些如激子相干实验、超辐射现象及二维光谱实验直接反应了系统的相干性的存在，并暗示量子相干与高效率输运的联系。然而，理论上已经大量研究的一些物理现象仍然还有一些争论，比如相干机制是否一定对高效率的输运起决定性的作用。此外，一些重要的物理机制仍然缺乏相应的研究，比如存在量子相变时，不同相区对激子输运的影响；存在外电场时，对集光系统的二维光谱或量子纠缠的研究；多激子在集光化合物的动力学演化等。因此，本项目对于进一步理解集光化合物复杂系统的量子动力学性质，对提高生物传输系统的输运效率都具有重要的理论指导意义。

项目完成情况：根据项目预期成果，我们完成了Holstein模型中激子动力学、线性吸收谱及二维光谱问题的相关研究，其成果已经正式发表SCI论文一篇。另外，我们利用非马尔科夫量子主方程研究了发色团（chromophore）在自旋玻璃态环境的动力学及线性吸收谱。. 取得的成果概述：（1）我们利用Davydov孤子理论研究了LH2单环系统激子的动力学演化、线性吸收谱及二维红外振动光谱（two-dimensional infrared vibrational spectroscopy），同时还研究了LH2环的不同构型、存在对角无序时及弛豫动力学对光谱结构的影响。我们的理论不仅补充了二维光谱的研究方法，而且具有比传统二维光谱研究方法更高效的计算效率。相关结果已经正式发表在Journal of Chemical Physics 139, 104103 (2013). （2）利用极化子变换及非马尔科夫量子主方程研究了发色团在低温自旋玻璃系统，其同时处在耗散环境的模型。这种方法可用于非平衡初始态的研究。我们采用相关实验数据研究了发色团（二能级）的动力学行为、与环境的纠缠及其线性吸收谱的特性，得到发色团在自旋环境及波色库的退相干机制。