Tichauer Ruth H, Feist Johannes, Groenhof Gerrit
Nanoscience Center and Department of Chemistry, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland.
Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, Spain.
J Chem Phys. 2021 Mar 14;154(10):104112. doi: 10.1063/5.0037868.
Coupling molecules to the confined light modes of an optical cavity is showing great promise for manipulating chemical reactions. However, to fully exploit this principle and use cavities as a new tool for controlling chemistry, a complete understanding of the effects of strong light-matter coupling on molecular dynamics and reactivity is required. While quantum chemistry can provide atomistic insight into the reactivity of uncoupled molecules, the possibilities to also explore strongly coupled systems are still rather limited due to the challenges associated with an accurate description of the cavity in such calculations. Despite recent progress in introducing strong coupling effects into quantum chemistry calculations, applications are mostly restricted to single or simplified molecules in ideal lossless cavities that support a single light mode only. However, even if commonly used planar mirror micro-cavities are characterized by a fundamental mode with a frequency determined by the distance between the mirrors, the cavity energy also depends on the wave vector of the incident light rays. To account for this dependency, called cavity dispersion, in atomistic simulations of molecules in optical cavities, we have extended our multi-scale molecular dynamics model for strongly coupled molecular ensembles to include multiple confined light modes. To validate the new model, we have performed simulations of up to 512 Rhodamine molecules in red-detuned Fabry-Pérot cavities. The results of our simulations suggest that after resonant excitation into the upper polariton at a fixed wave vector, or incidence angle, the coupled cavity-molecule system rapidly decays into dark states that lack dispersion. Slower relaxation from the dark state manifold into both the upper and lower bright polaritons causes observable photo-luminescence from the molecule-cavity system along the two polariton dispersion branches that ultimately evolves toward the bottom of the lower polariton branch, in line with experimental observations. We anticipate that the more realistic cavity description in our approach will help to better understand and predict how cavities can modify molecular properties.
将分子与光学腔的受限光模式耦合，在操纵化学反应方面显示出巨大潜力。然而，要充分利用这一原理并将腔体用作控制化学的新工具，就需要全面了解强光 - 物质耦合对分子动力学和反应性的影响。虽然量子化学可以提供对未耦合分子反应性的原子层面见解，但由于在此类计算中准确描述腔体存在挑战，探索强耦合系统的可能性仍然相当有限。尽管最近在将强耦合效应引入量子化学计算方面取得了进展，但应用大多局限于仅支持单一光模式的理想无损腔中的单个或简化分子。然而，即使常用的平面镜微腔的基模频率由镜子之间的距离决定，腔体能量也取决于入射光线的波矢。为了在光学腔中分子的原子模拟中考虑这种称为腔色散的依赖性，我们将用于强耦合分子系综的多尺度分子动力学模型进行了扩展，以纳入多个受限光模式。为了验证新模型，我们对红色失谐法布里 - 珀罗腔中多达512个罗丹明分子进行了模拟。我们的模拟结果表明，在以固定波矢或入射角共振激发到上极化激元后，耦合的腔 - 分子系统迅速衰减到缺乏色散的暗态。从暗态流形到上、下亮极化激元的较慢弛豫导致分子 - 腔系统沿着两个极化激元色散分支产生可观测的光致发光，最终朝着下极化激元分支的底部演化，这与实验观察结果一致。我们预计，我们方法中更现实的腔体描述将有助于更好地理解和预测腔体如何改变分子性质。
