Enhanced Homogeneity of Moire Superlattices in Double-Bilayer WSe2 Homostructure

Moire superlattices have emerged as a promising platform for investigating and designing optically generated excitonic properties. The electronic band structure of these systems can be qualitatively modulated by interactions between the top and bottom layers, leading to the emergence of new quantum phenomena. However, the inhomogeneities present in atomically thin bilayer moire superlattices created by artificial stacking have hindered a deeper understanding of strongly correlated electron properties. In this work, we report the fabrication of homogeneous moire superlattices with controllable twist angles using a 2L-WSe2/2L-WSe2 homostructure. By adding extra layers, we provide additional degrees of freedom to tune the optical properties of the moire superlattices while mitigating the nonuniformity problem. The presence of an additional bottom layer acts as a buffer, reducing the inhomogeneity of the moire superlattice, while the encapsulation effect of the additional top and bottom WSe2 monolayers further enhances the localized moire excitons. Our observations of alternating circularly polarized photoluminescence confirm the existence of moire excitons, and their characteristics were further confirmed by theoretical calculations. These findings provide a fundamental basis for studying moire potential correlated quantum phenomena and pave the way for their application in quantum optical devices.

Automated summary

This study reports the fabrication of homogeneous moire superlattices with controllable twist angles and the tuning of their optical properties using additional layers. The presence of these layers reduces the inhomogeneity of the superlattice and enhances the localized moire excitons. The existence of moire excitons is confirmed through experimental observations and theoretical calculations.