Polaritonic Huang–Rhys Factor: Basic Concepts and Quantifying Light–Matter Interactions in Media
Yu-Chen Wei and Liang-Yan Hsu*
Journal of Physical Chemistry Letters, 14, 9, 2395–2401 (2023).
The Huang–Rhys (HR) factor, a dimensionless factor that characterizes electron–phonon (vibronic) coupling, has been extensively employed to investigate a variety of material properties. In the same spirit, we propose a quantity called the polaritonic HR factor to quantitatively describe the effects of (i) light–matter coupling induced by permanent dipoles and (ii) dipole self-energy. The former leads to polaritonic displacements, while the latter is associated with the electronic coupling shift named reorganization dipole self-coupling. In the framework of macroscopic quantum electrodynamics, our theory can evaluate the polaritonic HR factor, reorganization dipole self-coupling, and modified light–matter coupling strength in an arbitrary dielectric environment without free parameters, whose magnitudes are in good agreement with the previous experimental results. We believe that this study provides a useful perspective on understanding and quantifying light–matter interactions in media.