Characterization of Exciton-exciton entanglement and correlations

TL;DR

This paper investigates the entanglement and correlations of excitons in many-body systems, especially under strong interactions, providing insights into when perturbation theories are valid and how excitonic phases behave in 1D materials.

Contribution

It offers a general framework to analyze exciton entanglement and correlations, extending understanding beyond bosonic approximations in strongly interacting regimes.

Findings

Perturbation theory remains valid for weakly entangled excitons.

Strong interactions lead to fermionic behavior in excitons.

Provides a phase diagram of exciton entanglement states in 1D systems.

Abstract

Excitons in the weakly interacting regime can be well-described by many-body perturbation theories such as the Bethe-Salpeter equation formalism. However, for materials such as transition metal dichalcogenides moir\'e heterostructures under strong illumination, with the emergence of dense excitonic states, the strong correlation and entanglement between electrons and holes may cause the many-body perturbation method to fail, and excitons may not be treated in the bosonic picture, but exhibit fermionic behaviors. In our work, we investigate the phase space where excitons, and the electrons and holes which constitute them, are weakly or strongly entangled, as well as their binding for different interaction profiles and the degree of localization of the electrons and holes. We corroborate the validity of using many-body perturbation theory in the exciton with interactions. Our work provides a general way to analyze the correlation and entanglement of multi-particle excitations in many-body systems, and gives a more comprehensive understanding of different phases for exciton entanglement and interactions in 1D systems.