Twist-dependent intra- and interlayer excitons in moire MoSe2 homobilayers

TL;DR

This study investigates how the twist angle in MoSe2 homobilayers influences moire coupling and exciton properties, revealing twist-dependent shifts, stacking effects, and exciton types with experimental and theoretical agreement.

Contribution

It provides a detailed analysis of twist-dependent intra- and interlayer excitons in MoSe2 homobilayers, combining experiments with a continuum model to elucidate moire effects.

Findings

Redshift of K-K and Γ-K excitons with small twist angles

Identification of two distinct intralayer moire excitons for R-stacking

Bright interlayer excitons at higher energies

Abstract

Optoelectronic properties of van der Waals homostructures can be selectively engineered by the relative twist angle between layers. Here, we study the twist-dependent moire coupling in MoSe2 homobilayers. For small angles, we find a pronounced redshift of the K-K and {\Gamma}-K excitons accompanied by a transition from K-K to {\Gamma}-K emission. Both effects can be traced back to the underlying moire pattern in the MoSe2 homobilayers, as confirmed by our low-energy continuum model for different moire excitons. We identify two distinct intralayer moire excitons for R-stacking, while H-stacking yields two degenerate intralayer excitons due to inversion symmetry. In both cases, bright interlayer excitons are found at higher energies. The performed calculations are in excellent agreement with experiment and allow us to characterize the observed exciton resonances, providing insight about the layer composition and relevant stacking configuration of different moire exciton species.