Dynamics of photosynthetic light harvesting systems interacting with N-photon Fock states
Dynamics of photosynthetic light harvesting systems interacting with N-photon Fock states
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DOI：
10.1063/5.0082822
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发表时间：
2022-06-28
影响因子：
4.4
通讯作者：
Whaley, K. Birgitta
中科院分区：
文献类型：
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作者：
Ko, Liwen;Cook, Robert L.;Whaley, K. Birgitta
在n光子Fock态脉冲的激励下，我们开发了一种方法来模拟实际光合作用光收集系统的激子动力学，包括非马尔可夫耦合到声子的自由度。该方法将运动形式的输入-输出和层次方程结合为双层次密度矩阵方程。分析表明，在与自然光合作用条件相关的弱场激发下，n光子Fock态输入和相应的相干态输入在激发流形中产生等密度矩阵。然而，与相干态输入产生的相干相比，n光子Fock态输入在基子空间和受激子空间之间没有引起非对角线相干。我们推导了有或没有声子影响时吸收单Fock态光子的概率表达式。对于短脉冲（或等效的宽带宽脉冲），我们表明吸收概率具有仅依赖于系统相关的有效能量扩散参数& uddelta的普遍行为；和激光耦合常数& UGamma；这适用于广泛的发色团系统和各种脉冲形状。我们还分析了在相反的长脉冲（窄带宽）状态下的吸收概率。然后，我们推导出声子存在时长时间发射率的表达式，并用它来研究集体发射与独立发射的区别。最后，我们给出了单光子激发下LHCII单体（14-mer）体系的数值模拟，说明了双层次方程的使用。
We develop a method to simulate the excitonic dynamics of realistic photosynthetic light harvesting systems, including non-Markovian coupling to phonon degrees of freedom, under excitation by N-photon Fock state pulses. This method combines the input-output and the hierarchical equations of motion formalisms into a double hierarchy of density matrix equations. We show analytically that under weak field excitation relevant to natural photosynthesis conditions, an N-photon Fock state input and a corresponding coherent state input give rise to equal density matrices in the excited manifold. However, an N-photon Fock state input induces no off-diagonal coherence between the ground and excited subspaces, in contrast with the coherences created by a coherent state input. We derive expressions for the probability to absorb a single Fock state photon with or without the influence of phonons. For short pulses (or, equivalently, wide bandwidth pulses), we show that the absorption probability has a universal behavior that depends only upon a system-dependent effective energy spread parameter & UDelta; and an exciton-light coupling constant & UGamma;. This holds for a broad range of chromophore systems and for a variety of pulse shapes. We also analyze the absorption probability in the opposite long pulse (narrow bandwidth) regime. We then derive an expression for the long time emission rate in the presence of phonons and use it to study the difference between collective vs independent emission. Finally, we present a numerical simulation for the LHCII monomer (14-mer) system under single photon excitation that illustrates the use of the double hierarchy equations.