Berry curvature contribution towards $ 1s-2p_{\pm} $ interlayer exciton ultrafast transition within a $R-WSe_{2}/MoSe_{2} $ heterobilayer

TL;DR

This paper investigates the Berry curvature effects on interlayer exciton spectra in WSe2/MoSe2 heterobilayers, revealing how quantum-geometric properties influence exciton splitting and enabling control of exciton states via optical methods.

Contribution

It demonstrates the impact of Berry curvature on interlayer exciton spectra and explores the tunability of excitonic transitions in heterobilayers with environmental and twist-angle variations.

Findings

Berry curvature causes splitting of $2p_+$ and $2p_-$ exciton states.

Dielectric environment and twist angle affect exciton spectra.

Long-lived $1s$ exciton state enables optical control of $2p_{\pm}$ states.

Abstract

We calculate the spectrum of interlayer neutral excitons in transition-metal-dichalcogenide WeSe$_2$/MoSe$_2$ heterobilayers in the $R$-stacking configuration. Most saliently, we show that, similarly to neutral excitons and trions in monolayer transition-metal dichalcogenides, the spectrum is sensitive to the Berry curvature and thus quantum-geometric effects underlying the electron and hole wave functions. Due to the spatial separation between the electron and hole constituting the exciton in different layers, the Berry-curvature-induced splitting of the between the $2p_+$ and the $2p_-$ exciton states is smaller than for monolayer excitons. Furthermore, we investigate the dependence of the exciton spectra on the dielectric environment and the twist angle between the two layers. Finally, the long-lived moir\'e interlayer exciton ground state ($1s$) enhances the possibility of creating brightened $2p_{\pm}$ states using a circularly polarized medium-infrared probe from the $1s$ ground state. As a result, we determine the polarizability of the $1s-2p_{\pm}$ transition, following by two-level dressed model for the optical Stark effect.