Spectroscopic properties under vibrational strong coupling in disordered matter from path-integral Monte Carlo...

Area of Science:

• Quantum Chemistry
• Spectroscopy
• Computational Physics

Background:

• Vibrational strong coupling (VSC) modifies molecular spectra and reactivity by coupling cavity optical resonance with molecular vibrations.
• VSC is an inherently collective phenomenon, requiring methods that capture multi-body interactions.

Purpose of the Study:

• Introduce Path Integral Monte Carlo (PIMC) simulations to model VSC, accounting for quantum effects and collective behavior.
• Develop a method to decompose hybrid optical-molecular states into constituent molecular modes.
• Validate PIMC against established models and exact diagonalization.

Main Methods:

• Utilized Path Integral Monte Carlo (PIMC) simulations with multiple molecular system replicas to capture collective effects.
• Employed the Pauli-Fierz Hamiltonian to model the coupling between disordered Morse oscillators and a single cavity.
• Analyzed the decomposition of hybrid states into bare molecular modes.

Main Results:

• PIMC simulations successfully reproduced known features of VSC, aligning with the Tavis-Cummings model.
• PIMC results showed excellent agreement with exact diagonalization for small systems.
• The collective mode coupled to the cavity exhibited harmonic oscillator behavior, consistent with the quantum central limit theorem, despite the anharmonicity of individual Morse oscillators.

Conclusions:

• PIMC is a powerful tool for simulating VSC, accurately capturing quantum and collective aspects.
• The method allows for the detailed analysis of hybrid states and their underlying molecular components.
• The emergence of harmonic behavior in the collective mode highlights fundamental quantum statistical properties in VSC systems.