Nonlinear Dynamics in the Formation of Molecular Polariton Condensates

TL;DR

This study uses ultrafast nonlinear optical techniques to investigate the rapid formation and underlying mechanisms of molecular polariton condensates, revealing new insights into their dynamics and potential for controlled applications.

Contribution

It introduces ECPL as a tool to directly observe femtosecond-scale condensation dynamics in molecular polariton systems, highlighting mechanisms beyond simple radiative scattering.

Findings

Condensation occurs within hundreds of femtoseconds.

A sustained population indicates additional feeding from higher momentum states.

ECPL provides quantitative insights into condensation timescales and mechanisms.

Abstract

Exciton-polaritons - hybrid light-matter quasiparticles - can undergo Bose-Einstein-like condensation at elevated temperatures owing to their lower effective mass. This becomes even more pronounced in the context of molecular polariton condensates where the large exciton binding energy of Frenkel excitons facilitates condensation at room temperature. While widely studied as low-threshold coherent light sources, the dynamics of their condensation remain poorly understood, partly due to the limitations of existing kinetic models. Here, we use excitation correlation photoluminescence (ECPL), a nonlinear optical technique with 220fs resolution, to probe molecular polariton condensation in Rhodamine-B-doped small-molecule ionic isolation lattices (SMILES). This platform promotes dipole alignment and suppresses detrimental intermolecular interactions. ECPL reveals condensate formation within hundreds of femtoseconds, driven by radiative scattering from the reservoir. A sustained population beyond the polariton lifetime suggests an additional feeding mechanism from higher momentum states in the lower polariton dispersion. These results provide quantitative insight into condensation timescales and mechanisms, advancing our control over polariton dynamics.