Influence of Interlayer Stacking on Optical Behavior in WSe$_{2}$/MoS$_{2}$ van der Waals Heterostructures

TL;DR

This study explores how the stacking arrangement in WSe₂/MoS₂ heterostructures influences excitonic properties, revealing diverse exciton types and guiding optical property engineering through layer orientation control.

Contribution

It provides a comprehensive analysis of the role of stacking symmetry in excitonic behavior, introducing principles for tailoring optical properties in van der Waals heterostructures.

Findings

Stacking symmetry determines excitonic nature and optical activity.

Multiple excitonic states including 2D, 3D, and charge-transfer are identified.

Interlayer hybridization and symmetry rules govern exciton dimensionality.

Abstract

We investigate the impact of crystal alignment on excitonic behavior in WSe$_{2}$/MoS$_{2}$ van der Waals heterostructures by comparing eclipsed (AA) and staggered (AB) stacking configurations. Our first-principles and symmetry-based analysis reveal that interlayer stacking symmetry plays a central role in determining the nature of electron-hole pairs. We uncover a rich variety of excitonic states, including spatially confined two-dimensional (2D) excitons, delocalized three-dimensional (3D) excitons, and charge-transfer (CT) excitons with interlayer character. The dimensionality and optical activity of these excitons are governed by the interplay among orbital character, interlayer hybridization, and symmetry-imposed selection rules. Our findings establish general principles for engineering excitonic properties in van der Waals heterostructures through controlled layer orientation and stacking order.