Anisotropic Excitonic Photoluminescence Observed on Artificial Bilayer MoS2 with Heterostrain

Abstract

In a moiré structure formed by isotropic semiconducting transition metal dichalcogenide (TMD), tuning the isotropic excitons to be anisotropic is quite challenging. Herein, by introducing controllable in-plane interlayer uniaxial strain to a MoS₂ monolayer (ML) and stacking it to another unstrained ML MoS₂, we successfully prepared an artificial bilayer (BL) moiré structure with heterostrain. The intralayer direct and indirect excitons within this structure demonstrate pronounced anisotropic photoluminescence (PL) emissions at both ambient and low temperatures. At 80 K, the PL anisotropic ratios of indirect and direct excitons can be enhanced to 1.45 and 1.31, respectively, in samples subjected to tensile heterostrain. These findings significantly advance our understanding of the anisotropic optical behaviors exhibited by moiré excitons of TMD materials, potentially paving the way for the design of future anisotropic twistronic devices.