非局域激子光学响应对单层过渡金属硫族化合物面内激子极化激元的影响
Influence of nonlocal excitonic optical response on in-plane exciton polaritons supported by monolayer transition-metal dichalcogenides
- Institute for Basic Science（基础科学研究院）
- RIKEN（理化学研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究发展非局域激子光学响应微观理论，研究hBN封装单层WS₂中面内激子极化激元，发现空间非局域性使色散向低波矢移动，产生更平滑且横向延伸的近场分布，并可通过hBN厚度调控多模式贡献。
AI中文摘要：
实现纳米尺度的光约束和长距离传播是纳米光子学中的一个核心挑战，对控制分子光物理过程和能量转移具有重要意义。单层过渡金属硫族化合物（TMDs）支持面内激子极化激元（IPEPs），这是一种在可见光范围内的深度亚波长光学模式。在此范围内，电磁场在长度尺度上与激子尺寸相当的变化，使得激子光学响应中的空间非局域性至关重要。在此，我们发展了一种非局域激子光学响应的微观理论，并研究了六方氮化硼（hBN）封装单层WS$_2$中IPEPs的近场性质。通过将两带大质量狄拉克费米子描述与广义莫特-瓦尼尔处理相结合，我们推导了一个非局域电敏感性，该敏感性同时考虑了激子的质心和内部相对运动。激子光学响应中的空间非局域性使极化激元色散相对于基于局域响应近似的结果向较低的面内波矢方向移动。这减少了高波矢贡献，并产生了更平滑的近场分布，这些分布在更大的横向距离上延伸，同时保持纳米尺度的约束。此外，在更高的激发能量下，多个激子极化激元模式在不同的波矢处贡献，并且它们的相对贡献可以通过改变覆盖hBN层的厚度来调节。这些见解阐明了空间非局域性在范德华异质结构极化激元性质中的基本作用。
英文摘要：
Achieving nanoscale light confinement and long-range propagation is a central challenge in nanophotonics, with important implications for controlling molecular photophysical processes and energy transfer. Monolayer transition-metal dichalcogenides (TMDs) support in-plane exciton-polaritons (IPEPs), deeply subwavelength optical modes in the visible range. In this regime, electromagnetic fields vary on length scales comparable to the exciton size, making spatial nonlocality in the excitonic optical response essential. Here, we develop a microscopic theory of the nonlocal excitonic optical response and investigate the near-field properties of IPEPs in hexagonal boron nitride (hBN)-encapsulated monolayer WS$_2$. Combining a two-band massive Dirac fermion description with a generalized Mott-Wannier treatment, we derive a nonlocal electric susceptibility that accounts for both the center-of-mass and internal relative motion of excitons. Spatial nonlocality in the excitonic optical response shifts the polariton dispersion toward lower in-plane wavevectors compared with the results based on the local-response approximation. This reduces high-wavevector contributions and produces smoother near-field distributions that extend over larger lateral distances while retaining nanoscale confinement. Furthermore, at higher excitation energies, multiple exciton-polariton modes contribute at distinct wavevectors, and their relative contributions can be tuned by varying the thickness of the capping hBN layer. These insights elucidate the fundamental role of spatial nonlocality in the polaritonic properties of van der Waals heterostructures.
