Interlayer and moir\'e excitons in atomically thin double layers: from individual quantum emitters to degenerate ensembles

TL;DR

This review discusses interlayer and moiré excitons in atomically thin bilayers, highlighting their unique properties, tunability, and potential for quantum applications, with a focus on transition metal dichalcogenides.

Contribution

It provides a comprehensive overview of the fundamental aspects and correlation phenomena of interlayer and moiré excitons in TMD bilayers, emphasizing their engineering potential.

Findings

Enlarged exciton binding energies and long lifetimes in TMD bilayers.

Moiré superlattices enable wide engineering of excitonic properties.

Strong correlation effects in dense exciton ensembles.

Abstract

Interlayer excitons (IXs), composed of electron and hole states localized in different layers, excel in bilayers composed of atomically thin van der Waals materials such as semiconducting transition metal dichalcogenides (TMDs) due to drastically enlarged exciton binding energies, exciting spin-valley properties, elongated lifetimes, and large permanent dipoles. The latter allows modification by electric fields and the study of thermalized bosonic quasiparticles, from the single particle level to interacting degenerate dense ensembles. Additionally, the freedom to combine bilayers of different van der Waals materials without lattice or relative twist angle constraints leads to layer hybridized and moir\'e excitons which can be widely engineered. This review covers fundamental aspects of IXs including correlation phenomena as well as the consequence of moir\'e superlattices with a strong focus on TMD homo- and hetero-bilayers.