Polariton Effects in Molecular Crystals Studied by Classical and Quantum-Electrodynamic Approaches

A quantum-electrodynamic approach is studied as an alternative to the classical description of polaritons in molecular crystals, with the focus on future interpretation of oligothiophene spectra. As expected, the results of the two approaches coincide, but the quantum description is better suited for future generalizations, notably for detailed studies of vibronic coupling. The quantum approach is used here to probe the importance of inherent polaritonic effects. They are found to be minor, being superseded by vibronic interactions; the latter are responsible for most peculiarities observed in oligothiophene spectra.