Polariton response in the presence of Brownian dissipation from molecular vibrations

TL;DR

This paper investigates how molecular vibrations and associated Brownian dissipation affect the polariton response in strongly coupled cavity-molecule systems, revealing limitations of the coupled oscillator model and providing detailed predictions for experimental conditions.

Contribution

It demonstrates the failure of the coupled oscillator model in describing polariton responses with molecular vibrations and offers a more accurate model considering non-Lorentzian dissipation effects.

Findings

Coupled oscillator model fails to capture non-Lorentzian dissipation effects.

Temperature influences polariton peak splitting and shape.

Predictions depend on molecular vibrational parameters and Rabi splitting size.

Abstract

We study the elastic response of a stationarily driven system of a cavity field strongly coupled with molecular excitons, taking into account the main dissipation channels due to the finite cavity linewidth and molecular vibrations. We show that the frequently used coupled oscillator model fails in describing this response especially due to the non-Lorentzian dissipation of the molecules to their vibrations. Signatures of this failure are the temperature dependent minimum point of the polariton peak splitting, uneven polariton peak height at the minimum splitting, and the asymmetric shape of the polariton peaks even at the experimentally accessed "zero-detuning" point. Using a rather generic yet representative model of molecular vibrations, we predict the polariton response in various conditions, depending on the temperature, molecular Stokes shift and vibration frequencies, and the size of the Rabi splitting. Our results can be used as a sanity check of the experiments trying to "prove" results originating from strong coupling, such as vacuum-enhanced chemical reaction rate.