Homogeneous moiré exciton emission in MoSe₂/WSe₂ heterolayers

Vertical stacking of two atomic layers with a small angle rotation and/or slight lattice mismatch give birth to moiré superlattice, which is a fertile ground for research of novel phases of excitons and electrons. However, the fabrication of high-quality moiré superlattice, particularly the interface involving transition metal dichalcogenides (TMD), has been a long-standing challenge. The complex inhomogeneous spectra put huge difficulty in analyzing the properties of moiré exciton. In this presentation, we will report homogeneous moiré exciton emission in large-area atomically clean TMD heterobilayers assembled under ultra-high vacuum, shed light on the origins of emission lines in moiré potentials. For a presentative MoSe₂/WSe₂ sample, distortions of moiré wavelength are found to be only a few percentages across the sample area about 10 μm². Furthermore, we observe homogeneous single narrow peak emission in two different samples, which show similar PL spectra at higher excitation power. The biexciton emission with attractive dipolar interaction emerges due to the delocalization of excitons in moiré superlattices. On the high energy side of exciton, we observe an exciton-phonon line. Our findings provide insights into moiré physics, accelerate further exploration of the properties and applications of TMD heterobilayers.