Spatially Modulated Moiré Potential in Twisted MoSe₂/MoS₂ Heterobilayers

Bo-Han Lin^1*, Yung-Chun Chao¹, Chien-Ju Li¹, Fu-Hsien Chu¹, Le-Chih Cho¹, Li-Syuan Lu¹, Jung-Jung Su¹, Wen-Hao Chang¹

¹Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan

* Presenter:Bo-Han Lin, email:evan0315lin@gmail.com

Twisted heterobilayers (hBLs) of transition metal dichalcogenides can form a moiré superlattice of periodically varying atomic registry between the two layers. The long periodicity moiré superlattice in real space leads to zone-folding in the momentum space, forming the moiré minibands, which causes drastic change to the excitonic states at small twist angles. For interlayer excitons, the effects of moiré periodicity can be even more remarkable since the electrons and holes are separated in different layers and the excitonic properties varies at different atomic registry. To study the twist-angle dependence, conventional methods based on mechanical exfoliation and transfer of individual crystals are tedious to fabricate many hBLs with various twist angles within 5°. Here we report on the study of moiré excitons in MoSe₂/MoS₂ hBLs fabricated by stacking a large MoSe₂ flake on an ensemble of highly-oriented MoS₂ flakes grown by chemical vapor deposition. The small angle variations in the MoS₂ flakes form a large number of hBLs with various small twist angles, enabling the study of twist-angle dependence of moiré excitons. We observed systematic energy shifts and fine structures in intralayer excitons with the twist angle, signifying the formation of moiré minibands. The spatially varying moiré potential confines the interlayer excitons at high symmetry points in the moiré superlattice. Since the selection rule of interlayer excitonic states alters at different atomic registry, the spatial distribution of interlayer excitons can be revealed by investigating the polarization dependence of each state. Understanding the twist-angle dependent properties of moiré excitons provides insights for future developments of “twistronics”.

Keywords: transition metal dichalcogenides, moiré potential, moiré superlattice, heterobilayer, twistronics