近日，美国宾夕法尼亚大学的Abraham Nitzan及其研究小组与美国亚利桑那州立大学的Joseph E. Subotnik合作并取得一项新进展。经过不懈努力，他们揭示了法布里-珀罗腔中极化子输运的性质。相关研究成果已于2024年3月19日在国际知名学术期刊《物理评论A》上发表。

在本文中，研究人员针对超快弹道输运现象进行了数值模拟，详细展示了从短、空间局域化脉冲初始化到初始化后在真实空间和时间中的演变过程。他们采用两种方法解决问题：一是适用于平面结构的标准传递矩阵法（TMM），二是基于麦克斯韦-布洛赫方程的数值解方法，适用于更一般的构型（如复杂超表面）和激励模式。当应用于多层平面结构时，TMM与麦克斯韦-布洛赫方程的数值计算结果高度一致，验证了这两种方法的有效性。

研究发现，分子激子在腔内的输运与腔内增强电磁场的演化同步进行。此外，同步输运率与通过宽频率范围内的色散关系计算得到的群速度相吻合。最后，研究人员将群速度与量子建模中的Hopfield系数联系起来，提出光-物质耦合对面内波矢量的依赖是理解极化子输运行为的关键因素，但此前常被忽视。这些模拟为揭示光和激子的集体运动提供了直观工具，有助于科学家更准确地解读极化子的实验观察结果。

据悉，法布里-珀罗微腔可以显著增强光与分子之间的相互作用，从而形成被称为极化子的混合光-物质状态。当分子与具有有限(非零)面内波矢量的腔模式共振时，极化子具有更小的有效质量和更大的群速度，从而产生长程和超快弹道输运的可能性。

附：英文原文

Title: Nature of polariton transport in a Fabry-Perot cavity

Author: Zeyu Zhou, Hsing-Ta Chen, Maxim Sukharev, Joseph E. Subotnik, Abraham Nitzan

Issue&Volume: 2024/03/19

Abstract: Fabry-Perot microcavities can strongly enhance interactions between light and molecules, leading to the formation of hybrid light-matter states known as polaritons. Polaritons possess much smaller effective masses and much larger group velocities when the molecules are resonant with cavity modes that have finite (nonzero) in-plane wave vectors, giving rise to the possibilities of long-range and ultrafast ballistic transport. In this paper, we present the results of numerical simulations of the ultrafast ballistic transport phenomenon in real space and time during and after initialization with a short, spatially localized pulse. We address this problem with two approaches: the standard transfer-matrix method (TMM) for planar structures and a second simulation based on the numerical solution of the Maxwell-Bloch equations that can be used for general configurations (complex metasurfaces, for instance) and excitation modes. The agreement between the TMM and the full numerical calculation with the Maxwell-Bloch equations when applied to multilayer planar configurations provides proof of the validity of both approaches for the present analyses. Overall, we find that the transport of the molecular excitons inside the cavity synchronize with the evolution of the enhanced electromagnetic field inside the cavity. Moreover, the synchronized transport rate is in good agreement with the group velocities predicted from a calculated dispersion relation across a wide range of frequencies. Finally, we relate the group velocity to the Hopfield coefficient obtained from quantum modeling and suggest that the dependence of light-matter coupling on the in-plane wave vector can be an important but overlooked factor for understanding the transport behavior of polaritons. These simulations provide an intuitive tool for understanding the collective motion of light and excitons and helps us to better understand how experimental observations of polaritons should be interpreted.

DOI: 10.1103/PhysRevA.109.033717

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.033717