发表机构
Center for Quantum Technology Research, and Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology（北京理工大学物理学院，量子技术研究中心，先进光电子量子架构与测量教育部重点实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过构造精确双激子Bloch态和平面波拟设，完整求解了有限尺寸Merrifield链中的双激子问题，解析描绘了支持双激子束缚态的参数区域，证明最多存在两种位于散射连续谱上方或下方的束缚态，并定量解释了其随波数的演化。
AI 中文摘要
理解双激子束缚态（BSs）的形成与动力学对于利用多激子现象和设计下一代有机半导体材料至关重要。尽管诸如分子间激子-激子相互作用或多能级分子内构型等多种机制可以产生这些束缚态，但其底层晶格动力学的基本理解仍是一个关键挑战。在此背景下，Merrifield激子模型作为捕捉单点双激发态与双粒子散射连续谱之间复杂量子混合的首要框架脱颖而出。在本工作中，通过构造一组精确的双激子Bloch态并应用平面波拟设来处理由此产生的不均匀三对角矩阵，我们为有限尺寸Merrifield链中的双激子问题提供了完整且严格的解。我们解析地描绘了支持双激子束缚态的参数区域，证明最多可以出现两种不同类型的束缚态，它们位于散射连续谱的上方或下方。此外，我们定量解释了这两种束缚态如何随整个布里渊区内的总波数演化。所得到的本征能量和波函数的闭式表达式为探索相关分子聚集体中的激子动力学和光学响应提供了有价值的基准。
英文摘要
Understanding the formation and dynamics of two-exciton bound states (BSs) is crucial for harnessing multi-exciton phenomena and designing next-generation organic semiconductor materials. While various mechanisms such as intermolecular exciton-exciton interactions or multi-level intramolecular configurations can generate these BSs, a fundamental understanding of their underlying lattice dynamics remains a key challenge. Within this context, the Merrifield exciton model stands out as a premier framework for capturing the intricate quantum mixing between single-site doubly-excited states and two-particle scattering continuum. In this work, by constructing a set of exact two-exciton Bloch states and applying a plane-wave ansatz to treat the resulting inhomogeneous tridiagonal matrices, we provide a complete, rigorous solution to the two-exciton problem in a finite-size Merrifield chain. We analytically map the parameter regions that support two-exciton BSs, proving that at most two distinct types of BSs can emerge, located either above or below the scattering continuum. Furthermore, we provide a quantitative interpretation of how these two types of BSs evolve as a function of the total wave number within the whole Brillouin zone. The obtained closed-form expressions for the eigenenergies and wave functions offer valuable benchmarks for exploring exciton dynamics and optical responses in related molecular aggregates.
Comments12 pages, 6 figures, to appear in Phys. Rev. B
