Twist Angle Tuning of Moir\'{e} Exciton Polaritons in van der Waals Heterostructures

TL;DR

This paper investigates how twist angle in van der Waals heterostructures influences moiré exciton polaritons, revealing tunable hybrid light-matter states with potential for engineered quantum metamaterials.

Contribution

It introduces a microscopic model combining excitonic density matrix and Hopfield approach to show twist angle control over polariton properties in heterostructures.

Findings

Exciton-light coupling strength varies with twist angle.

Number of polariton branches can be tuned via twist angle.

Hybrid states become delocalized due to light and higher-energy exciton mixing.

Abstract

Twisted atomically thin semiconductors are characterized by moir\'{e} excitons. Their optical signatures and selection rules are well understood. However, their hybridization with photons in the strong coupling regime for heterostructures integrated in an optical cavity has not been in the focus of research yet. Here, we combine an excitonic density matrix formalism with a Hopfield approach to provide microscopic insights into moir\'{e} exciton polaritons. In particular, we show that exciton-light coupling, polariton energy, and even the number of polariton branches can be controlled via the twist angle. We find that these new hybrid light-exciton states become delocalized relative to the constituent excitons due to the mixing with light and higher-energy excitons. The system can be interpreted as a natural quantum metamaterial with a periodicity that can be engineered via the twist angle. Our study presents a significant advance in microscopic understanding and control of moir\'{e} exciton polaritons in twisted atomically thin semiconductors.