Chirality and dimensionality in the ultrastrong light-matter coupling regime

TL;DR

This paper explores how the dimensionality of molecular systems influences chiroptical properties in the ultrastrong light-matter coupling regime, revealing unique effects in 2D configurations absent in 3D bulk systems.

Contribution

It demonstrates the critical role of dimensionality in chiroptical effects within the ultrastrong coupling regime, introducing a gyrotropic coupling mechanism specific to 2D systems.

Findings

Differential polaritonic energy shifts occur in 2D chiral systems due to gyrotropic coupling.

3D bulk configurations do not exhibit the same differential shifts.

The 2D effect is physically analogous to a particle in a magnetic field undergoing cyclotron motion.

Abstract

We unveil the key-role of dimensionality in describing chiroptical properties of molecules embedded inside an optical Fabry-P\'erot cavity. For a 2D-layer configuration, we show that the interplay between molecular chirality and spatial dispersion of the cavity-modes, results in a gyrotropic coupling $\chi$ at the origin of a differential shift in polaritonic energy-spectra. This differential shift is proportional to $\chi$, while for 3D bulk-aggregate configurations it is shown to vanish. We interpret physically the former 2D-chiral effect by analogy with the classical Newtonian motion of a fictive particle in presence of 3D restoring force, and static magnetic field. The gyrotropic coupling is shown to directly perturbate the anholonomy angle of the classical trajectories, and the fictive particle undergoes cyclotron gyrations upon entering the ultrastrong light-matter coupling regime.