Interlayer vibrational hybrid normal mode enabling molecular chiral phonons

TL;DR

This paper reports the discovery of a chiral phonon mode in a molecular-inorganic interface, revealing new hybrid vibrational states that could enable phonon chirality in molecular superlattices.

Contribution

It introduces a novel hybrid vibrational mode in a molecular-inorganic interface, identified through first-principles calculations, demonstrating potential for phonon chirality control.

Findings

Discovery of an infrared-active chiral phonon mode in MoSe₂ with pyrene molecules

Hybrid mode results from molecular rotation and substrate optical phonon coupling

Potential to enable phonon chirality in molecular superlattices

Abstract

Organic/inorganic interfaces formed by monolayer substrates and conjugated molecular adsorbates are attractive material platforms leveraging the modularity of organic compounds together with the long-range phenomena typical of condensed matter. New quantum states are known to be generated by electronic interactions in these systems as well as by their coupling with light. However, little is still known about hybrid vibrational modes. In this work, we discover from first principles the existence of an infrared-active chiral phonon mode in a pyrene-decorated MoSe$_{2}$ monolayer given by the combination of a frustrated rotation of the molecule around its central axis and an optical mode in the substrate. Our results suggest the possibility to enable phonon chirality in molecular superlattices.