[论文解读] Coherent Biexciton Transport in the Presence of Exciton-Exciton Annihilation in Molecular Aggregates

Rajesh Dutta, Chern Chuang|arXiv (Cornell University)|Mar 4, 2026

Spectroscopy and Quantum Chemical Studies被引用 0

一句话总结

论文开发了一个简化密度矩阵框架，处理跨激发鼓风格的群组之中的粒子与相干性，以研究分子聚集体中的双激子动力学和激子–激子湮灭，强调初始态相干性与动量作为运输与发射的关键控制参数。

ABSTRACT

We present a theoretical framework for biexciton dynamics in molecular aggregates that explicitly treats populations and coherences across excitation manifolds within a reduced density-matrix formalism. By extending kinetic descriptions beyond the weak-coupling limit, the approach captures the influence of exciton delocalization and exciton-exciton annihilation while remaining computationally tractable within a Markovian description of environmental relaxation. Using this framework, we investigate how the spatial profile and momentum composition of the initial biexciton state govern fluorescence decay and transport. Incoherent initial conditions lead to strongly non-exponential relaxation and time-dependent diffusion driven by nonlinear population kinetics. In contrast, coherently prepared biexciton states exhibit pronounced early-time coherent transport, whose character depends sensitively on whether the initial state is prepared as a standing-wave or traveling-wave superposition of single-exciton modes. Despite nearly identical emission dynamics for J and H aggregate, biexciton transport properties differ markedly due to band structure-dependent interference effect. Our results demonstrate that biexciton dynamics remains strongly influenced by initial-state coherence and momentum composition. Besides initial-state preparation, the coherent-to-incoherent crossover and the diffusive spreading of the exciton density are sensitive to internal conversion processes such as exciton fusion and the decay to the first excited state. The present work establishes initial-state preparation as a key control parameter for many-exciton transport in excitonic systems and provides a general framework for interpreting nonlinear optical experiments beyond population-based descriptions.

研究动机与目标

• 将动力学描述扩展到中等与强耦合体系，以捕捉多激子动力学中的相干效应。
• 在可处理的马尔可夫框架中显式包含激发结构内外的相干性。
• 研究初始双激子态的空间轮廓和动量组成如何影响荧光衰减与传输。
• 为超越基于种群描述的非线性光学实验提供通用解释框架。

提出的方法

• 用每分子三个能级的哈密顿量（基态、第一激发态、第二激发态）来建模双激子动力学。
• 采用Lindblad型马尔可夫主方程投影到简化密度矩阵元。
• 引入跨跨膜耦合V(12)以解释驱动激子–激子湮灭的融合/分解过程。
• 推导对角密度矩阵元（P_m, N_m）及非对角密度矩阵元（W_mn, Z_mn, R_mn）的运动方程。
• 对四体相关量进行平均场型因式分解以闭合非线性速率方程。
• 将May的动力学框架推广以包含弱耦合极限之外的时变相干性。

Figure 1: Biexciton dynamics in linear chain of three-level systems with nearest neighbor interaction. $J$ is the interaction between first excited state, $\mathcal{J}$ refers to second excited state interaction and $K$ denotes fusion due to exciton-exciton annhiliation.

实验结果

研究问题

• RQ1 初始双激子空间分布和动量分布如何影响J-与H-聚集体中的相干传输与发射？
• RQ2 激子–激子湮灭在塑造非线性、时变的弛豫与扩散中的作用如何？
• RQ3 内部转换过程，如激子融合与向第一激发态的衰变，如何影响多激子动力学中的相干‑无相干转变？
• RQ4 相干性与跨膜相关性是否会显著改变相对于仅基于种群的描述的传输？

主要发现

• 初始态为驻波或行进波的单激子模态叠加时，早期相干传输得到增强或被改变。
• 双激子传输与发射动力学对能带结构和干涉效应高度敏感，J-与H聚集体之间存在显著差异。
• 在无相干初始条件下，非线性种群动力学驱动时间依赖的扩散；而相干初始态表现出显著的非指数行为。
• 框架揭示初始态相干性与动量组成仍是多激子传输的关键控制参数，超越简单的种群模型。
• 内部转换过程（包括激子融合与衰变路径）显著影响观测到的扩散与相干动力学。