Sokolovskii Ilia, Tichauer Ruth H, Morozov Dmitry, Feist Johannes, Groenhof Gerrit
Nanoscience Center and Department of Chemistry, University of Jyväskylä, P.O. Box 35, Jyväskylä, 40014, Finland.
Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, Spain.
Nat Commun. 2023 Oct 19;14(1):6613. doi: 10.1038/s41467-023-42067-y.
Exciton transport can be enhanced in the strong coupling regime where excitons hybridize with confined light modes to form polaritons. Because polaritons have group velocity, their propagation should be ballistic and long-ranged. However, experiments indicate that organic polaritons propagate in a diffusive manner and more slowly than their group velocity. Here, we resolve this controversy by means of molecular dynamics simulations of Rhodamine molecules in a Fabry-Pérot cavity. Our results suggest that polariton propagation is limited by the cavity lifetime and appears diffusive due to reversible population transfers between polaritonic states that propagate ballistically at their group velocity, and dark states that are stationary. Furthermore, because long-lived dark states transiently trap the excitation, propagation is observed on timescales beyond the intrinsic polariton lifetime. These insights not only help to better understand and interpret experimental observations, but also pave the way towards rational design of molecule-cavity systems for coherent exciton transport.
在激子与受限光模式杂化形成极化激元的强耦合 regime 中，激子传输可以得到增强。由于极化激元具有群速度，它们的传播应该是弹道式的且范围很长。然而，实验表明有机极化激元以扩散方式传播，且比其群速度传播得更慢。在这里，我们通过对法布里 - 珀罗腔中罗丹明分子的分子动力学模拟来解决这一争议。我们的结果表明，极化激元的传播受腔寿命限制，并且由于在以其群速度弹道式传播的极化激元态与静止的暗态之间的可逆布居转移，看起来是扩散的。此外，由于长寿命暗态会短暂捕获激发，所以在超过固有极化激元寿命的时间尺度上观察到了传播。这些见解不仅有助于更好地理解和解释实验观测结果，还为合理设计用于相干激子传输的分子 - 腔系统铺平了道路。
