Cavity-induced Non-Adiabatic Dynamics and Spectroscopy of Molecular Rovibrational Polaritons studied by Multi-Mode Quantum Models

TL;DR

This paper presents a theoretical study of rovibrational polaritons in a diatomic molecule-cavity system, revealing conical intersections, hybrid states, and spectroscopic features influenced by cavity interactions and dissipation.

Contribution

It introduces a multi-mode quantum model capturing non-adiabatic rovibrational dynamics and spectroscopy of polaritons, highlighting the role of conical intersections and hybrid states.

Findings

Identification of vibro-polaritonic conical intersections (VPCIs).

Observation of multi-peak spectral progression linked to hybrid states.

Dissipative effects cause peak broadening and intensity reduction.

Abstract

We study theoretically the quantum dynamics and spectroscopy of rovibrational polaritons formed in a model system composed of a single rovibrating diatomic molecule, which interacts with two degenerate, orthogonally polarized modes of an optical Fabry-P\'erot cavity. We employ an effective rovibrational Pauli-Fierz Hamiltonian in length gauge representation and identify three-state vibro-polaritonic conical intersections (VPCIs) between singly-excited vibro-polaritonic states in a two-dimensional angular coordinate branching space. The lower and upper vibrational polaritons are of mixed light-matter hybrid character, whereas the intermediate state is purely photonic in nature. The VPCIs provide effective population transfer channels between singly-excited vibrational polaritons, which manifest in rich interference patterns in rotational densities. Spectroscopically, three bright singly-excited states are identified, when an external infrared laser field couples to both a molecular and a cavity mode. The non-trivial VPCI topology manifests as pronounced multi-peak progression in the spectral region of the upper vibrational polariton, which is traced back to the emergence of rovibro-polaritonic light-matter hybrid states. Experimentally ubiquitous spontaneous emission from cavity modes induces a dissipative reduction of intensity and peak broadening, which mainly influences the purely photonic intermediate state peak as well as the rovibro-polaritonic progression.