Simulating molecular polaritons in the collective regime using few-molecule models

Area of Science:

• Quantum Chemistry and Spectroscopy
• Computational Physics
• Materials Science

Background:

• Simulating molecular polaritons beyond simple models is computationally intensive due to high dimensionality and complex molecular dynamics.
• Existing models often oversimplify molecular behavior or are limited to small numbers of molecules.
• Understanding the interplay of electronic and nuclear degrees of freedom is crucial for accurate polariton dynamics.

Purpose of the Study:

• To develop a computationally efficient method for simulating large ensembles of molecular polaritons.
• To provide an intuitive framework for understanding polariton chemistry and reactivity.
• To enable the design of robust strategies for controlling chemical reactions using light-matter interactions.

Main Methods:

• Exploitation of permutational symmetries to reduce computational cost in ab initio quantum dynamics simulations.
• Discovery of an emergent hierarchy of timescales allowing approximation with an effective single molecule.
• Systematic derivation of finite N corrections and introduction of the collective dynamics using truncated equations (CUT-E) approach.

Main Results:

• The CUT-E method drastically reduces computational cost for large N molecular ensembles.
• An effective single-molecule approximation becomes exact as N approaches infinity, with systematic finite N corrections.
• The approach accurately models polariton relaxation rates and cavity-assisted energy funneling between molecular species.

Conclusions:

• CUT-E provides a computationally efficient and intuitive formalism for studying molecular polaritons.
• The method facilitates seamless modification of single-molecule models for ensemble dynamics.
• This work offers a pathway to understanding and controlling chemical reactivity through engineered light-matter interactions in polariton chemistry.