Linear response of molecular polaritons

Area of Science:

• Quantum Optics
• Condensed Matter Physics
• Spectroscopy

Background:

• Collective light-matter strong coupling involves N molecular emitters interacting with a photon mode in an optical cavity.
• This regime is crucial for understanding phenomena like molecular polaritonics.

Purpose of the Study:

• To develop a simplified theoretical framework for analyzing light-matter strong coupling.
• To derive analytical expressions for optical spectra in this regime.
• To connect concepts from open quantum systems and linear response theory to molecular polaritonics.

Main Methods:

• Mapping the collective light-matter strong coupling regime to a quantum impurity model.
• Approximating an anharmonic bath with an effective harmonic bath in the thermodynamic limit (N ≫ 1).
• Deriving analytical expressions for linear optical spectra (transmission, reflection, absorption) using molecular linear susceptibility.

Main Results:

• The complex system simplifies to coupled harmonic oscillators.
• Analytical formulas for optical spectra are derived, requiring only molecular linear susceptibility as input.
• The formalism accounts for temperature, disorder, vibronic coupling, and optical saturation.

Conclusions:

• The developed formalism provides a powerful and simplified approach to studying light-matter strong coupling.
• It unifies existing results and offers new interpretations connecting open quantum systems theory with molecular polaritonics.
• The method is applicable to both linear and certain nonlinear optical experiments.