Controlling the Manifold of Polariton States Through Molecular Disorder

TL;DR

This paper investigates how molecular disorder affects exciton polariton states, developing a new theoretical approach to describe strong light-matter coupling in disordered organic materials, with implications for manipulating material properties.

Contribution

It introduces a generalized method to analyze polariton states in disordered systems, challenging existing ideas about ultrastrong coupling with broad absorbers.

Findings

Disorder redistributes photonic character within polariton states

The new approach captures key spectroscopic features in disordered systems

Challenges the notion that ultrastrong coupling requires ordered materials

Abstract

Exciton polaritons, arising from the interaction of electronic transitions with confined electromagnetic fields, have emerged as a powerful tool to manipulate the properties of organic materials. However, standard experimental and theoretical approaches overlook the significant energetic disorder present in most materials now studied. Using the conjugated polymer P3HT as a model platform, we systematically tune the degree of energetic disorder and observe a corresponding redistribution of photonic character within the polariton manifold. Based on these subtle spectral features, we develop a more generalized approach to describe strong light-matter coupling in disordered systems that captures the key spectroscopic observables and provides a description of the rich manifold of states intermediate between bright and dark. Applied to a wide range of organic systems, our method challenges prevailing notions about ultrastrong coupling and whether it can be achieved with broad, disordered absorbers.