Discrimination of Chiral and Helical Contributions to Raman Scattering of Liquid Crystals using Vortex Beams

TL;DR

This study employs vortex photon fields with orbital and spin angular momentum to distinguish chiral and helical contributions in Raman scattering of liquid crystals, revealing insights into their chiral fluctuations and quasiparticle dynamics.

Contribution

It introduces a novel method using vortex beams to separate chiral and helical effects in Raman scattering, advancing characterization techniques for liquid crystals.

Findings

Identification of chiral and helical Raman components based on scattering vector and topological charge

Observation of anomalous dispersion linked to angular momentum transfer

Detection of roton-like quasiparticles due to competing interactions

Abstract

We use vortex photon fields with orbital and spin angular momentum to probe chiral fluctuations within liquid crystals. In the regime of iridescence with a well-defined pitch length of chirality, we find low energy Raman scattering that can be decomposed into helical and chiral components depending on the scattering vector and the topological charge of the incident photon field. Based on the observation of an anomalous dispersion we attribute quasi-elastic scattering to a transfer of angular momenta to roton-like quasiparticles. The latter are due to a competition of short-range repulsive and long-range dipolar interactions. Our approach using a transfer of orbital angular momentum opens up an avenue for the advanced characterization of chiral and optically active devices and materials.