Exciton-phonon scattering and photo-excitation dynamics in J-aggregate microcavities

TL;DR

This paper presents a model for exciton-phonon interactions and photo-excitation dynamics in J-aggregate microcavities, accurately reproducing experimental photoluminescence features and elucidating relaxation bottlenecks and vibrational effects.

Contribution

A novel theoretical model describing exciton-polariton dynamics in J-aggregate microcavities, incorporating disorder, vibrational relaxation, and photoluminescence behavior.

Findings

Accurately reproduces the photoluminescence intensity ratio between polariton branches.

Identifies relaxation bottleneck at the excitonic reservoir bottom as key to thermal activation.

Shows vibrational modes significantly influence relaxation and emission processes.

Abstract

We have developed a model accounting for the photo-excitation dynamics and the photoluminescence of strongly coupled J-aggregate microcavities. Our model is based on a description of the J-aggregate film as a disordered Frenkel exciton system in which relaxation occurs due to the presence of a thermal bath of molecular vibrations. In a strongly coupled microcavity exciton-polaritons are formed, mixing superradiant excitons and cavity photons. The calculation of the microcavity steady-state photoluminescence, following a CW non resonant pumping, is carried out. The experimental photoluminescence intensity ratio between upper and lower polariton branches is accurately reproduced. In particular both thermal activation of the photoluminescence intensity ratio and its Rabi splitting dependence are a consequence of the bottleneck in the relaxation, occurring at the bottom of the excitonic reservoir. The effects due to radiative channels of decay of excitons and to the presence of a paritticular set of discrete optical molecular vibrations active in relaxation processes are investigared.