Anomalous bright narrow interlayer exciton photoluminescence in MoSe₂-WSe₂ heterostructures

Van der Waals heterostructures provide a new platform for studying spatially indirect interlayer excitons, where the constituent electrons and holes are located in different layers. These heterostructures are made by stacking two or more two-dimensional materials via a polymer stamping technique. Stacking layers with a lattice mismatch and/or twist angle between layers will form a moiré pattern in real space. This moiré lattice can modulate the exciton energy, resulting in so-called moiré excitons where excitons are trapped at the moiré potential minima. Recent studies on - heterostructures have shown narrow lines in low power photoluminescence(PL), which were attributed to moiré excitons. Optical measurements of our high-quality - heterostructures encapsulated by hBN shows an anomalous bright narrow interlayer exciton PL localized to a small area of the sample. The PL of this structure shows interlayer PL emission whose linewidth is comparable to delocalized interalayer excitons in high quality samples. We will discuss the density and temperature dependence of this bright interlayer exciton PL and how it relates to other recent reports of interlayer moiré excitons in transition metal dichalcogenide heterostructures.